Acromag Busworks 900mb series User manual

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Find the Acromag BusWorks 917MB-0900 at our website: Click HERE

BusWorks



900MB Series

Modbus/RS485 Network I/O Modules

Model 917MB-0900 Quad Current Output

Model 918MB-0900 Quad Voltage Output

USER’S MANUAL

ACROMAG INCORPORATED

30765 South Wixom Road

P.O. BOX 437

Wixom, MI 48393-7037 U.S.A.

Tel: (248) 295-0880

Fax: (248) 624-9234

Data and specifications are subject to change without notice.

8500-633-J12F005

BusWorksModel 917MB/918MB Network I/O Module User’s Manual Quad Current/Voltage Output

___________________________________________________________________________________________

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Safety Summary – Symbols on equipment:

Means “Caution, refer to this manual for additional

information”.

The information contained in this manual is subject to change

without notice. Acromag, Inc., makes no warranty of any kind

with regard to this material, including, but not limited to, the

implied warranties of merchantability and fitness for a particular

purpose. Further, Acromag, Inc., assumes no responsibility for

any errors that may appear in this manual and makes no

commitment to update, or keep current, the information contained

in this manual. No part of this manual may be copied or

reproduced in any form, without the prior written consent of

Acromag, Inc.

Table of Contents

Page

1.0

INTRODUCTION

………………………………..…….. 2

DESCRIPTION ………………………………………… 2

Key 917MB/918MB Features…..………………….. 3

ACCESSORY ITEMS …………………………………. 3

900MB Configuration Software (5034-186).…….... 3

RS232-to-RS485 Serial Converter (5034-214).….. 3

Interface Cable (5034-202)…….……..…………….. 4

Software Interface Package (900C-SIP)………….. 4

2.0

PREPARATION FOR USE

….……………………….. 4

UNPACKING AND INSPECTION ……………………

MODULE INSTALLATION.……………..…………….. 4

Default Mode Switch………………………………… 4

Mounting ……………………………………………… 4

Electrical Connections ……………………………… 4

SOFTWARE INSTALLATION ……………….……….. 5

3.0

MODULE CONFIGURATION

……………………….. 5

MODULE CALIBRATION……………………………… 8

AN INTRODUCTION TO MODBUS………………….. 9

MODULE SOFTWARE CONFIGURATION…………. 15

OUTPUT CALIBRATION….………………..…………. 20

4.0

THEORY OF OPERATION

………………………….. 21

5.0

SERVICE AND REPAIR

..…………………………… 21

SERVICE AND REPAIR ASSISTANCE ……………. 21

PRELIMINARY SERVICE PROCEDURE ..…………. 21

TROUBLESHOOTING………………………………… 21

6.0

SPECIFICATIONS

……………………………………. 21

MODEL NUMBER DEFINITION……………………… 21

ANLOG OUTPUT SPECIFICATIONS …………..….. 22

DIGITAL OUTPUT SPECIFICATIONS………………. 23

ENCLOSURE/PHYSICAL SPECIFICATIONS …….. 23

APPROVALS ………………………………………….. 23

ENVIRONMENTAL SPECIFICATIONS….………….. 23

COMMUNICATION INTERFACE SPECIFICATIONS 24

CONFIGURATION AND CONTROLS..……………… 24

SOFTWARE CONFIGURATION……..…………….… 25

List of Drawings Page

Simplified Schematic (4501-828)…..…….……………..… 26

Functional Block Diagram (4501-829)………………….… 26

Network Connections (4501-805)…………..…….………. 27

Electrical Connections (4501-831)……..………….……… 27

Interposing Relay Conn. & Contact Pro. (4501-832)……. 28

Enclosure Dimensions (4501-833) …………………..…… 28

Windows 95/98 & NT are registered trademarks of Microsoft

Corporation. Modbus is a registered trademark of Modicon, Inc.

IMPORTANT SAFETY CONSIDERATIONS

It is very important for the user to consider the possible adverse

effects of power, wiring, component, sensor, or software failures

in designing any type of control or monitoring system. This is

especially important where economic property loss or human life

is involved. It is important that the user employ satisfactory

overall system design. It is agreed between the Buyer and

Acromag, that this is the Buyer’s responsibility.

1.0 INTRODUCTION

These instructions cover the hardware functionality of the

transmitter models listed in Table 1. Supplementary sheets are

attached for units with special options or features.

Table 1: Models Covered in This Manual

Series/

Input/Type

Options/Output/

Enclosure/Approvals

Factory

Configuration

917MB -0900 -C

918MB -0900 -C

Notes (Table 1):

1. Agency approvals include CE, UL Listed, and cUL Listed.

2. Include the “-C” suffix to specify factory configuration option.

Otherwise, no suffix is required for standard configuration.

DESCRIPTION

The Acromag 900MB family is a group of process I/O

modules and accessories for Modbus/RS485 network I/O

applications. The Model 917MB-0900 and 918MB-0900 provide

control of four analog output channels, plus four digital output

channels, via an isolated RS485 network I/O path utilizing the

industry standard Modbus protocol. The Model 917MB drives

four channels of process current, while the 918MB drives four

channels of voltage output signals. Both models also include four

control outputs for simple ON/OFF control of external devices.

The 917/918MB modules contain an advanced technology

microcontroller with integrated downloadable flash and EEPROM

memory for non-volatile program, configuration, calibration, and

parameter data storage. Units are fully reconfigurable via our

user-friendly Windows 95/98



or NT



Configuration Program and

the RS485 interface, or other compatible Modbus software. Once

configured, these modules may operate as an active RS485

network slave connected to other modules and a host computer.

Each module provides four isolated analog outputs for DC

process current or voltage signals. The module uses four 12-bit

DAC’s to generate separate channel voltage signals. In addition,

four open-drain mosfets provide discrete control of external

devices. Outputs may be automatically programmed to user-

defined levels or states following a watchdog timer timeout. The

open-drain outputs include yellow LED’s at the front of the

module that provide visual indication of output state. Additionally,

a green “Run” and yellow “Status” LED provide local feedback of

operating mode, system diagnostics, watchdog status, and

module status.

All 900MB modules are designed to withstand harsh

industrial environments. They feature RFI, EMI, ESD, EFT, and

surge protection, plus low temperature drift, wide ambient

temperature operation, and isolation between signal I/O, power,

and the network. They also have low radiated emissions per CE

requirements.

BusWorksModel 917MB/918MB Network I/O Module User’s Manual Quad Current/Voltage Output

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As wide-range DC-powered devices, these units may be

powered from DC power networks incorporating battery backup.

Since input power is diode-bridge coupled, the unit may be

connected to redundant power supplies, or several units may

safely share a single DC supply. The unit may also be powered

from common 24VAC power.

Units are DIN-rail mounted and removable terminal blocks

facilitate ease of installation and replacement, without having to

remove wiring. Transmitter power, network, and digital output

wiring are inserted at one side of the unit, while analog output

wiring is inserted at the other side. Plug-in connectors are an

industry standard screw clamp type that accept a wide range of

wire sizes.

Flexible transmitter functionality, network reprogrammability,

mixed signal I/O, and a network interface, all combine in a single

package to make this instrument extremely powerful and useful

over a broad range of applications. Further, the safe, compact,

rugged, reconfigurable, and reliable design of this transmitter

makes it an ideal choice for control room or field applications.

Custom module configurations are also possible (please consult

the factory).

Key 918MB Module Features:

•Agency Approvals – CE, UL, & cUL Listed.

•Easy Windows



Configuration – Fully configurable via our

user-friendly Windows 95/98



or NT



900MB Configuration

Program.

•RS485/Modbus Network Interface – This proven high

speed interface is highly immune to noise, can operate over

long distances, and allows a large number of modules to be

networked together. The unit communicates using the

industry-standard Modbus command/response protocol.

•Nonvolatile Reprogrammable Memory – This module has

an advanced technology microcontroller with integrated,

non-volatile, downloadable flash memory and EEPROM.

This allows the functionality of this device to be reliably

reprogrammed thousands of times.

•Fully Isolated – Output circuitry, network, & power are

isolated from each other for safety and noise immunity.

•Discrete Outputs – High voltage and current, open-drain

mosfets provide direct control of external devices. Outputs

may be controlled independently, or via watchdog timeout.

•Flexible Process Current Output (917MB) – Generates up

to four process current signals in three ranges.

•Flexible DC Voltage Output (918MB) – Generates up to

four DC voltage signals in three ranges.

•Watchdog Timer – An output watchdog timer function is

included and may be configured for timeout periods up to

65534 seconds (18.2 hours). Timer will timeout if a read or

write operation to any I/O channel does not occur over the

configured time period. Outputs may be automatically set to

user-defined levels or states following a watchdog timeout..

•Self-Diagnostics – Built-in routines operate upon power-up

for reliable service, easy maintenance, and troubleshooting.

A watchdog timer is also built into the microcontroller that

causes it to initiate a self reset if the controller ever “locks

up” or fails to return from an operation in a timely manner.

•High-Speed Data Rates – Supports RS485 communication

rates up to 115K baud.

•Wide Ambient Operation – The unit is designed for reliable

operation over a wide ambient temperature range.

Key 918MB Module Features…continued:

•Wide-Range DC-Power or 24VAC Power – This device

receives power over a wide supply range and the power

terminals are diode coupled. This makes this transmitter

useful for systems with redundant supplies, and/or battery

back-up. Additionally, the power terminals are not polarized.

•Hardened For Harsh Environments – The unit will operate

reliably in harsh industrial environments and includes

protection from RFI, EMI, ESD, EFT, and surges, plus low

radiated emissions per CE requirements.

•Convenient Mounting, Removal, & Replacement – The

DIN-rail mount and plug-in type terminal blocks make

module removal and replacement easy.

•High-Resolution Precise D/A Conversion – Transmitters

include high-resolution, low noise, Digital-to-Analog

Converters for high accuracy and reliability.

•LED Indicators – A green LED indicates power. A yellow

status LED will flash if the unit is placed in the default

communication mode. It will also flash rapidly upon

watchdog timeout. A yellow output LED indicates the

ON/OFF state of the associated open-drain output.

•Default Communication Mode – A push-button switch is

provided to set the module to a default set of communication

parameters for baud rate, module address, parity, and

number of stop bits. This provides a convenient way of

establishing communication with the module when its

internal settings are unknown.

ACCESSORY ITEMS

The following accessories are available from Acromag.

Acromag also offers other standard and custom transmitter types

to serve a wide range of applications (please consult the factory).

900MB Configuration & Control Software (Model 5034-186)

Series 900MB modules are configured with this user-friendly

Windows 95/98



or NT



Configuration Program. Optionally, any

software that supports the Modbus/RTU protocol may be used to

configure and control Series 900MB modules, but the use of this

software makes getting started easier. All module functions are

programmable and downloadable to the modules via this

software. The software also includes on-line help. Non-volatile

memory provides program and configuration storage within the

module. Note that this software may be optionally downloaded

from our website (www.acromag.com) to registered owners of

Series 900MB modules.

RS-232 to RS-485 Serial Adapter (Model 5034-214)

This device is a non-isolated, port-powered, signal converter

for communication between the RS-232 serial port of a personal

computer and the RS-485 network interface of Series 900MB I/O

Modules. It is used in conjunction with the Acromag

Configuration Software for simple reconfiguration, testing, and

troubleshooting of Series 900MB I/O modules. As a port-

powered device, it is not intended for driving fully loaded RS-485

networks over long distances, and does not have sufficient power

to drive terminated networks. The adapter has DB-9F connectors

at both ends and plugs directly into the common DB-9M serial

port connector of most personal computers. The module is

connected to the RS-485 side of this adapter via a separate

interconnecting cable (see Cable 5034-202 described below).

BusWorksModel 917MB/918MB Network I/O Module User’s Manual Quad Current/Voltage Output

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Interface Cable (Model 5034-202)

An 8-foot, 3-wire cable used to connect the RS-485 side of

Signal Converter 5034-214 to the RS-485 network terminals of

900MB modules. This cable has a DE-9M connector on one end,

with three stripped & tinned wires on the other end, labeled A, B,

& C for connection to module D, Dbar, & COM, respectively.

Series 900MB Software Interface Package (Model 900C-SIP)

The 900C-SIP Software Interface Package combines the

900MB Configuration Software (5034-186), RS-232 to RS-485

Serial Converter (5034-214), Interface Cable (5034-202), and

Instructions (8500-649), into a complete kit for interfacing with

Series 900MB I/O Modules.

2.0 PREPARATION FOR USE

UNPACKING AND INSPECTION

Upon receipt of product, inspect the shipping carton for

evidence of mishandling during transit. If shipping carton is badly

damaged or water stained, request that the carrier’s agent be

present when the carton is opened. If the carrier’s agent is

absent when the carton is opened, and the contents of the carton

are damaged, keep the carton and packing material for the

agent’s inspection. For repairs to a product damaged in

shipment, refer to the Acromag Service Policy to obtain return

instructions. Salvageable shipping cartons & packing material

should be saved for future use if the product must be shipped.

This module is physically protected with

packing material and electrically

protected with an anti-static bag during

shipment. It is recommended the

module be visually inspected for

evidence of mishandling prior to applying

power. This circuit utilizes static

sensitive components and should only be

handled at a static-safe workstation.

MODULE INSTALLATION

This transmitter utilizes a general purpose plastic enclosure.

Use an auxiliary enclosure to protect the unit in unfavorable

environments or vulnerable locations, or to maintain conformance

to applicable safety standards. Stay within the unit’s operating

temperature range. As shipped, unit is calibrated for all valid

input ranges and has the defaults shown in Table 2 below:

WARNING: Applicable IEC Safety Standards may require that

this device be mounted within an approved metal enclosure or

sub-system, particularly for applications with exposure to voltages

greater than or equal to 75VDC or 50VAC.

Table 2: 918MB Default Factory Configuration

PARAMETER

CONFIGURATION/CALIB

Module Address 247

Baud Rate 9600bps

Parity None (2 stop bits w/No parity)

Stop Bits 1 or 2 (When Parity=None)

Response Delay 0 (No Delay)

Output Range (Each Out) 0-20mA (917MB); 0-10V (918MB)

Watchdog Time 0 (Timer Disabled)

Analog Timeout Level 0 (Each Output)

Discrete Timeout State 1/ON (Each Output)

Notes (Table 2):

1. Do not confuse the Default Factory Configuration noted

above with the Default Communication Mode, which refers

to the fixed baud rate, module address, parity, and stop bit

settings achieved by pushing the Default Mode button until

the yellow status LED flashes ON/OFF. The Default

Communication Mode will temporarily over-ride any factory

configuration of baud rate, module address, parity, and stop

bits with settings of 9600bps, 247, None, and 2,

respectively. It is provided as a convenient means of

achieving communication with a module when these

parameters are unknown.

Your application will typically differ from the default factory

configuration and will require that the transmitter be reconfigured

to suit your needs. This can be easily accomplished with

Acromag’s user-friendly Windows 95/98



or NT



900MB

Configuration Program. Configuration is normally done prior to

field installation. Refer to MODULE SOFTWARE

CONFIGURATION of Section 3.0 for detailed instructions.

Default Mode Switch

A push-button default mode switch (DFT) and status LED are

provided at the front of the module as a convenient way of

communicating with the module when its baud rate and address

settings are unknown. Push and hold this button until the Status

LED flashes ON/OFF to indicate the module is in the Default

Communication Mode with a fixed module address of 247, baud

rate of 9600bps, no parity, and 2 stop bits. It is most convenient

to configure a module in this mode, then leave the default mode

by pressing this button again until the Status LED stops flashing

(constant ON or OFF), or by resetting the module. The Default

Mode is disabled following a software or power-on reset. New

communication parameters (baud rate, address, & parity) will

take effect following a module reset after leaving the Default

Mode.

Mounting

Refer to Enclosure Dimensions Drawing 4501-833 for mounting

and clearance dimensions.

DIN Rail Mounting: This module can be mounted on “T” type

DIN rails. Use suitable fastening hardware to secure the DIN rail

to the mounting surface. Units may be mounted side-by-side on

1-inch centers for limited space applications.

“T” Rail (35mm), Type EN50022: To attach, angle the top of the

unit towards the rail and locate the top groove of the adapter over

the upper lip of the rail. Firmly push the unit towards the rail until

it snaps solidly into place. To remove module, first separate the

input terminal block(s) from the bottom side of the module to

create a clearance to the DIN mount area. Next, insert a screw-

driver into the lower arm of the DIN connector and use it as a

lever to force the connector down until it disengages from the rail.

Electrical Connections

Analog output, digital output, and network & power terminals

can accommodate wire from 12-24 AWG, stranded or solid

copper. Strip back wire insulation ¼-inch on each lead before

installing into the terminal block. Analog output wiring should be

shielded twisted-pair. Since common mode voltages can exist on

signal wiring, adequate wire insulation should be used and proper

wiring practices followed.

BusWorksModel 917MB/918MB Network I/O Module User’s Manual Quad Current/Voltage Output

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It is recommended that analog output wiring, digital output wiring,

network wiring, and power wiring be separated from each other

for safety, as well as for low noise pickup. Note that terminal

blocks are a plug-in type and can be easily removed to facilitate

module removal or replacement, without removing individual

wires. Be sure to remove power before unplugging the terminals

to uninstall the module, or before attempting service. All

connections must be made with power removed.

CAUTION:

Risk of Electric Shock – More than one

disconnect switch may be required to de-energize the

equipment before servicing.

1. Power: Refer to Electrical Connections Drawing 4501-831.

Variations in power supply voltage within rated limits has

negligible effect on module accuracy. For supply

connections, use No. 14 AWG wires rated for at least 75°C.

The power terminals are diode bridge-coupled and not

polarized. The unit is powered from 10-36VDC, or 24VAC.

2. Analog Outputs: Connect outputs per Electrical

Connections Drawing 4501-831. Observe proper polarity

when making connections (see label for output type).

Note: Analog outputs go to their minimum levels following a

software or power-on reset of the module. Outputs may be

optionally sent to user-defined levels following a watchdog

timer timeout.

3. Digital Outputs (Coils): All discrete outputs are the open-

drains of n-channel mosfets whose source terminals share

return (RTN). Externally wired drain pullups or other load is

generally required. All outputs include transient voltage

suppressers and integrated snubbers, but may require

additional protection when switching inductive loads (see

below). Refer to the SPECIFICATIONS section for output

specifications and see the module side label for terminal

designations. Note that these outputs are for current-sinking

(low-side switching) applications only. Digital outputs are

turned OFF following a software or power-on reset of the

module, but can be optionally programmed to user-defined

states following a watchdog timer timeout. Observe proper

polarity when making connections. The output circuitry as a

group is electrically isolated from the network and power

circuits. If necessary, an interposing relay can be used to

switch higher currents as illustrated in the Interposing Relay

Connection Drawing 4501-832.

Note: Digital outputs go to their OFF state following a

software or power-on reset of the module. Outputs may be

optionally sent to user-defined states following a watchdog

timer timeout.

IMPORTANT – Protection With Inductive Loads: The

output mosfets have integrated shunt diode clamps

connected from drain to source to help protect the output

switch from damaging reverse emf voltages that exist when

controlling inductive loads. You may need to add external

protection local to the inductive load for added protection

and to prevent this emf from being distributed across the

connection media. For DC inductive loads, place a diode

across the load (1N4006 or equivalent) with cathode to (+)

and anode to (-).

4. Network Connections: Wire network as shown in Network

Connections Drawing 4501-805. Network common (COM)

should connect to earth ground at one point.

5. Grounding: See Electrical Connections Drawing 4501-831.

The module housing is plastic and does not require an earth

ground connection.

WARNING:

For compliance to applicable safety and

performance standards, the use of shielded cable is

recommended as shown in Drawing 4501-831. Further, the

application of earth ground must be in place as shown in

Drawing 4501-831. Failure to adhere to sound wiring and

grounding practices may compromise safety & performance.

SOFTWARE INSTALLATION – USING SETUP.EXE

The 900MB Configuration Software (Model 900C-SIP) is used

to configure Series 900MB modules and is installed as follows:

1. Start Windows 95/98/NTand insert the 900MB

Configuration Software CDROM into your drive D: (E: or M).

IMPORTANT: Before continuing with the installation

sequence, be sure to exit any other Windows programs that

may be running.

2. Click on the [START] button in the lower left hand corner of

the Windows screen. Then click on the “Run…” icon.

3. In the Run dialogue box, type d:\setup (or e:\setup) in the

Open field and click on [OK]. The setup program will

execute the Installshield Wizard.

You may need to click on the “Setup.exe” icon of the install

shield to proceed. On some machines, the setup.exe

program is not started automatically.

4. From the introductory Acromag 900MB Setup Screen, click

on [Next>] to proceed.

5. At this point, the 900MB Setup program will prompt you for

your “Name” and “Company”. Fill in this information, then

click on [Next>].

6. Now you will be prompted for a destination directory. You

may click on [Browse] to change the default directory, or

[Next>] to accept “C:\ProgramFiles\Acromag\900MB” as the

default. You may also click on [Back] to return to the prior

screen and make any changes.

7. At this point you will be prompted for a program folder name.

You may type a new name, use the scroll bar to select an

existing program folder, or click on [Next>] to accept the

“Acromag 900MB” default folder name.

8. Now you will be presented with your selections and you

should verify if they are correct. Press [Next>] to continue

and begin copying files, or press [Back] to return to prior

screens and make any changes.

9. After the Configuration Program files have been copied to

your hard drive, you will be prompted to click on [Finish] to

complete the setup.

10. Now click on the [Acromag 900MB] program folder icon at

the bottom of your windows screen, then click on the

Acromag 900MB program icon to start the Configuration

Program (Programs-Acromag 900MB-Acromag 900MB

Configuration icon).

3.0 MODULE CONFIGURATION

This module needs to be configured for your application.

This is easily accomplished using Acromag’s Windows 95/98



Modbus Configuration Software and an RS232-to-RS485

signal converter. The Acromag software is not required to

communicate with the Series 900MB, as any software capable of

sending Modbus network protocol commands over an RS485

network can be used. However, this software provides an easy

Windows format for communicating with the module that does not

require advanced familiarity with the Modbus protocol.

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Modbus registers are organized into the following reference

types identified by the leading number of the reference address:

Reference

Description

0xxxx Read/Write Discrete Outputs or Coils. A 0x

reference address is used to drive output data to

a digital output channel.

1xxxx Read Discrete Inputs. The ON/OFF status of a 1x

reference is controlled by the corresponding

digital input channel.

3xxxx Read Input Registers. A 3x reference register

contains a 16-bit number received from an

external source—e.g. an analog signal.

4xxxx Read/Write Output or Holding Registers. A 4x

(binary or decimal), or to send the data from the

CPU to an output channel.

Notes (Register Map):

1. The “x” following the leading character represents a four-

digit address location in user data memory. The leading

character is generally implied by the function code and

omitted from the address specifier for a given function. The

leading character also identifies the I/O data type.

2. The ON/OFF state of discrete inputs and outputs is

represented by a 1 or 0 value assigned to an individual bit in

a 16-bit data word. This is sixteen 0x or 1x references per

data word. With respect to mapping, the LSB of the word

maps to the lowest numbered channel of a group and

channel numbers increase sequentially as you move

towards the MSB. Unused bits are set to zero.

Modbus functions operate on register map registers to

configure and control modules. The following table outlines the

I/O modules. You will find it helpful to review this map as you

review the Modbus function descriptions later.

Model 917MB-0900 and 918MB-0900 Register Map

Ref Addr. Description Data Type/Format

Coil Registers (0x References, Read/Write)

0001

Thru

00004

0-3

(0000-

0003)

Four

Discrete

Outputs 0-3,

Program

States

Discrete Output Value.

Addresses a specific bit of

a 16-bit word that controls/

monitors the ON/OFF

status for the output.

Note:

This signal corresponds to

the gate signal of the n-channel

output mosfet. Thus, a read of

this register may not reflect the

actual output level at the drain of

the mosfet if the open-drain is not

pulled up or is left floating (no

excitation). Excitation must be

provided in order to operate the

outputs.

After reset, these registers read 0

(outputs OFF) and these

registers are not maintained in

EEPROM.

A set bit (1) means the

corresponding output is

ON. A clear bit (0) means

the corresponding output is

OFF. The bit position

corresponds to the output

channel number (i.e. output

0 uses bit 0 of the 16-bit

word at address 0, output 1

uses bit 1 of the 16-bit

word at address 1, etc.)

Unused bits of a word are

set to 0.

Bits 15-4: Not Used.

Additionally, unused bits

in range 3-0 are set to 0.

Model 917MB-0900 and 918MB-0900 Register Map

Ref Addr. Description Data Type/Format

Input Registers (3x References, Read-Only)

0001 0

(0000)

Module

Status

Bit 15: Flash Checksum

1 = Error Flag

0 = No Flash Error

Bit 14: Not Used l

Bit 13: Default Mode

1 = Default Mode Indicator

0 = Not In Default Mode

Bits 12-1: Zero

Bit 0: Watchdog Fault

1 = Watchdog Timeout

0 = Timeout Cleared

0002 1

(0001)

CH 0

Status Value

(917MB)

Bits 15-2: Zero

Bits 1,0: Output Range

00 = 0 = 0-20mA

01 = 1 = 4-20mA

10 = 2 = 0-1mA

11 = 3 = Reserved

0002 1

(0001)

CH0

Status Value

(918MB)

Bits 15-2: Zero

Bits 1,0: V-Output Range

00 = 0 = 0-10V

01 = 1 = 0-5V

10 = 2 = 0-1V

11 = Reserved

0003 2

(0002)

CH 1

Status Value

Format Is Same As CH 0

0004 3

(0003)

CH 2 Status

Value

Format Is Same As CH 0

0005 4

(0004)

CH 3 Status

Value

Format Is Same As CH 0

0006 5

(0005)

CH0 Raw

Count

Raw DAC Count Value

(See CALIBRATION)

0007 6

(0006)

CH1 Raw

Count

Raw DAC Count Value

(See CALIBRATION)

0008 7

(0007)

CH2 Raw

Count

Raw DAC Count Value

(See CALIBRATION)

0009 8

(0008)

CH3 Raw

Count

Raw DAC Count Value

(See CALIBRATION)

Holding Registers (4x References, Read/Write)

0001 0

(0000)

Slave

Address

Default=247

1-247

0002 1

(0001)

Baud Rate

Default=2,

9600bps

0 = 2400bps

1 = 4800bps

2 = 9600bps (Default)

3 = 14400bps

4 = 19200bps

5 = 28800bps

6 = 38400bps

7 = 57600bps

8 = 76800bps

9 = 115200bps

0003 2

(0002)

Parity

Default=

0, None

0 = No Parity Check

1 = Odd Parity Checking

2 = Even Parity Checking

0004 3

(0003)

Output

Watchdog

Time

Default=0,

Disabled

Can be set from 1 to 65534

seconds. Set to 65535

(FFFFH) or 0 (0000H) to

disable the watchdog timer.

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Model 917MB-0900 and 918MB-0900 Register Map

Ref Addr. Description Data Type/Format

Holding Registers (4x References, Read/Write)

40005 4

(0004)

Digital

Output

Channel

Watchdog

Timeout

States

Default=

65535,

Disabled

The four lower order bits of

this 16-bit register define

the state output channels

will be programmed to

following a watchdog

timeout. Timeout control of

outputs takes precedence

over alarm and direct

control. Bit 0 corresponds

to channel 0, bit 1 to

channel 1, bit 2 to channel

2, and bit 3 to channel 4.

Write 65535

Note: Clearing a timeout via an

I/O read or write does not return

the output(s) to their initial state

or level. They remain at their

timeout state or level until

otherwise written.

(FFFFH) to this register to

leave the outputs

unchanged following a

timeout (this is also the

default value).

0006 5

(0005)

Response

Delay Time

(Turnaround

Delay)

Default=0,

No Delay

Can be set from 0 to 65500

ticks (1 tick = 1.085us) and

represents the additional

delay the module will wait

before responding to a

message from the host.

Increase this value if you

have communication

trouble with the module or

you encounter a high

degree of error messages.

0007 6

(0006)

CH 0

Output Value

Default=0

Percentage (%) - Note 2.

After reset, this register

reads 0 and this register is

not maintained in

EEPROM.

0008 7

(0007)

CH 0

Timeout

Value

Default=0

Percentage (%) – Note 2.

Write 32767 (7FFFH) to

leave output unaffected by

a watchdog timeout.

0009 8

(0008)

CH0

Output

Configuration

(917MB)

Default=0,

0-20mA

Bits 15-2: Zero

Bits 1,0: I-Output Range

00 = 0 = 0-20mA

01 = 1 = 4-20mA

10 = 2 = 0-1mA

11 = Reserved

Note that the 0-20mA

range may not precisely go

to the 0mA endpoint. It will

typically approach 0mA

within 0.1%.

0009 8

(0008)

CH0

Output

Configuration

(918MB)

Default=0,

10V

Bits 15-2: Zero

Bits 1,0: V-Output Range

00 = 0 = 0-10V

01 = 1 = 0-5V

10 = 2 = 0-1V

11 = Reserved

0010 9

(0009)

CH 1

Output Value

Default=0

Percentage (%) - Note 2.

After reset, this register

reads 0 and this register is

not maintained in

EEPROM.

Model 917MB-0900 and 918MB-0900 Register Map

Ref Addr. Description Data Type/Format

Holding Registers (4x References, Read/Write)

0011 10

(000A)

CH 1

Timeout

Value

Default=0

Percentage (%) – Note 2.

Write 32767 (7FFFH) to

leave output unaffected by

a watchdog timeout.

0012 11

(000B)

CH1 Output

Configuration

(917MB)

Default=0,

0-20mA

Bits 15-2: Zero

Bits 1,0: I-Output Range

00 = 0 = 0-20mA

01 = 1 = 4-20mA

10 = 2 = 0-1mA

11 = Reserved

Note that the 0-20mA

range may not precisely go

to the 0mA endpoint. It will

typically approach 0mA

within 0.1%.

0012 11

(000B)

CH1 Output

Configuration

(918MB)

Default=0,

10V

Bits 15-2: Zero

Bits 1,0: V-Output Range

00 = 0 = 0-10V

01 = 1 = 0-5V

10 = 2 = 0-1V

11 = Reserved

0013 12

(000C)

CH 2

Output Value

Default=0

Percentage (%) -

See Note 2.

0014 13

(000D)

CH 2

Timeout

Value

Default=0

Percentage (%) – Note 2.

Write 32767 (7FFFH) to

leave output unaffected by

a watchdog timeout.

0015 14

(000E)

CH2

Output

Configuration

(917MB)

Default=0,

0-20mA

Bits 15-2: Zero

Bits 1,0: I-Output Range

00 = 0 = 0-20mA

01 = 1 = 4-20mA

10 = 2 = 0-1mA

11 = Reserved

Note that the 0-20mA

range may not precisely go

to the 0mA endpoint. It will

typically approach 0mA

within 0.1%.

0015 14

(000E)

CH2

Output

Configuration

(918MB)

Default=0,

10V

Bits 15-2: Zero

Bits 1,0: V-Output Range

00 = 0 = 0-10V

01 = 1 = 0-5V

10 = 2 = 0-1V

11 = Reserved

0016 15

(000F)

CH 3

Output Value

Default=0

Percentage (%) -

See Note 2.

0017 16

(0010)

CH 3

Timeout

Value

Default=0

Percentage (%) – Note 2.

Write 32767 (7FFFH) to

leave output unaffected by

a watchdog timeout.

0018 17

(0011)

CH3

Output

Configuration

(917MB)

Default=0,

0-20mA

Bits 15-2: Zero

Bits 1,0: I-Output Range

00 = 0 = 0-20mA

01 = 1 = 4-20mA

10 = 2 = 0-1mA

11 = Reserved

Note that the 0-20mA

range may not precisely go

to the 0mA endpoint. It will

typically approach 0mA

within 0.1%.

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Model 917MB-0900 and 918MB-0900 Register Map

Ref Addr. Description Data Type/Format

Holding Registers (4x References, Read/Write)

0018 17

(0011)

CH3

Output

Configuration

(918MB)

Default=0,

10V

Bits 15-2: Zero

Bits 1,0: V-Output Range

00 = 0 = 0-10V

01 = 1 = 0-5V

10 = 2 = 0-1V

11 = Reserved

0019 18

(0012)

Calibration

Access

And

Alternate

Method of

Module

Reset

Writing 24106 (5E2AH)

here immediately removes

write protection from the

calibration registers that

follow. All other values

apply write protection to the

calibration registers (except

41429).

Writing 41429 (A1D5H) to

this register will cause an

immediate module reset.

This is provided as an

alternate method of Reset

for software that does not

support the Reset Slave

(08) command.

After a reset, this register

reads 0 (write protection

enabled and no reset).

This register is not

maintained in EEPROM.

0020 19

(0013)

CH0 Cal

High Value

Raw DAC Value Register

(See CALIBRATION)

0021 20

(0014)

CH0 Cal

Low Value

Raw DAC Value Register

(See CALIBRATION)

0022 21

(0015)

CH1 Cal

High Value

Raw DAC Value Register

(See CALIBRATION)

0023 22

(0016)

CH1 Cal

Low Value

Raw DAC Value Register

(See CALIBRATION)

0024 23

(0017)

CH2 Cal

High Value

Raw DAC Value Register

(See CALIBRATION)

0025 24

(0018)

CH2 Cal

Low Value

Raw DAC Value Register

(See CALIBRATION)

0026 25

(0019)

CH3 Cal

High Value

Raw DAC Value Register

(See CALIBRATION)

0027 26

(001A)

CH3 Cal

Low Value

Raw DAC Value Register

(See CALIBRATION)

1001

This block

mirrors 1xxxx

registers.

Refer to Note 6. 1xxxx

Discrete Input Registers

are mapped to the 41xxx

Holding Register space

using an address offset of

41000.

2001

This block

mirrors 0xxxx

registers.

Refer to Note 6. 0xxxx Coil

Registers are mapped to

the 42xxx Holding Register

space using an address

offset of 42000.

3001

This block

mirrors 3xxxx

registers.

Refer to Note 5. 3xxxx

Input registers are mapped

to the 43xxx Holding

address offset of 43000.

Notes (Register Map):

1. Note that the Report Slave ID and Reset Slave functions do

not operate on Register Map locations.

2. Output values are indicated in percent-of-span units

represented by a 16-bit signed integer value with resolution

of 0.005%/lsb. The range is –163.84% (-32768 decimal) to

+163.835% (+32767 decimal). For example, -100%, 0%

and +100% are represented by the decimal values –20000,

0, and 20000, respectively. Clearing a watchdog timeout

does not return an output to its pre-timeout level, it remains

at its timeout level until otherwise written.

3. Configuration variables stored in holding registers (4xxxx

reference addresses) are maintained in EEPROM, except

for the Calibration Access & Reset Register and Output

Value Registers. Changes to configuration registers do not

take effect until the next software or power-on reset.

4. WARNING: Access to shaded register entries is normally

not required and writes to these registers should be avoided

to prevent module miscalibration.

5. For your convenience, this module mirrors the contents and

operation of 3xxxx registers into 43xxx holding register

space for systems and controllers that cannot directly

access 3xxxx register address space. That is, the 3xxxx

registers of this model can be written to, or read from, using

either the standard methods described in the Modbus

specification, or through mapping (mirroring) to the Holding

and you only need to offset your address by 43000. For

example: if you want to read Input Register 1 through the

Holding Registers, you would use the “Read Holding

Registers” function with an address of 43001.

6. For modules with a firmware revision later than G (as in

9300-037G of 917MB, or 9300-028G of 918MB), the

mirroring function as described in Note 5 is augmented as

follows (0xxxx also maps to 42xxx space, and 1xxxx also

maps to 41xxx space):

For 1xxxx Input Status Registers (where supported), the

return data is reformatted to match the Holding Register

format. For example, if you request Input Status for 12

digital inputs, instead of getting 2 bytes returned with the

first 12 bits representing 12 digital inputs, you will get 12

separate words (2 bytes) instead, with each set to 0000H

(OFF) or FFFFH (ON).

For 0xxxx Coil Registers (where supported), reads are

handled in the same way as noted for 1xxxx Input Status

Registers. That is, you may write to the coil registers using

the “Preset Single Register” function with an address offset

of 42000. Setting the data to 0000H will turn the coil OFF,

while setting the data to FF00H will turn the coil ON.

MODULE CALIBRATION

These analog out modules are calibrated using a single base

output range with fixed calibration points. Calibration of the sub-

ranges are interpolated based on these results. Prior to cal,

917MB units must have the 0-20mA output range selected, and

918MB units must have the 0-10V range selected. Calibration is

performed by adjusting the output signal until its measured value

precisely matches the low or high cal point. With the output level

precisely adjusted to the low or high cal point, the output

channel’s raw DAC Count is then read from the module (registers

30006-30009 in Memory Map). This same value is then written to

the corresponding channel’s respective Cal High or Cal Low

will have to write 24106 into the Calibration Access register to be

able to modify the Cal High/Low registers. This process is

repeated for the opposite calibration point.

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After writing the required values to the Cal Low & Cal High

registers of the output, new output calibration takes effect

immediately following a module reset. For best results, allow

some settling time between Low & High calibration and always

calibrate the low calibration point first.

Output Calibration Values For 917MB/918MB

Output

Factory Calibration LOW Point

Range

Output

Output %

DAC Count

20mA

4.000mA 4000 723

10V

0.000V 0 50

Output

Factory Calibration HIGH Point

Range

Output

Output %

DAC Count

20mA

20.000mA 20000 3614

10V

10.000V 20000 3609

Note that 917MB units have the 0-20mA output range

selected during calibration, while 918MB units have the 0-10V

output range selected during calibration. The output % value and

DAC count of the table are based on “ideal” conditions and will

only approximate random selected performance.

IMPORTANT: Because calibration of the module’s sub-ranges

are interpolated based on the primary range calibration noted

above, and because resolution is degraded for the sub-ranges, it

is very important that high accuracy be ensured for the primary

range calibration when making output adjustments and

measuring the output levels. Further, resolution limits of the

output sub-ranges may make it difficult to accurately adjust the

output level to the ideal range endpoints (especially for 0-1mA

and 0-1V output ranges). The inability to precisely attain

endpoint values will increase total error at the endpoints.

AN INTRODUCTION TO MODBUS

This section provides a description of the Modbus protocol

and the Modbus functions that apply to this model. The Modbus

protocol provides an industry standard method Series 900MB

modules use for parsing messages. Modbus devices

communicate using a master-slave technique in which only one

device (the master) can initiate transactions (called queries). The

other devices are slaves and respond by supplying the requested

data to the master, or by taking the action requested in the query.

Series 900MB modules are the slaves, and a typical master is a

host computer running appropriate application software. Masters

can address individual slaves, or initiate a broadcast message to

all slaves. Slaves return a response to all queries addressed to

them individually, but no response is returned to broadcast

queries from a master device.

Remote Terminal Unit (RTU) Mode

Series 900MB modules use the widely accepted Modbus

network protocol in the RTU (Remote Terminal Unit) serial

transmission mode. In RTU mode, each 8-bit message byte

contains two 4-bit hexadecimal characters, and is transmitted in a

continuous stream. The RTU mode byte format is shown below:

RTU Mode Byte Format

Coding System 8-bit binary, hexadecimal 0-9, A-F, two

hexadecimal characters contained in each

8-bit field of the message.

Bits Per Byte 1 start bit + 8 data bits, lsb sent first + 1bit

for even/odd parity or no bit for no parity +

1 stop bit if parity is used or 2 stop bits

with no parity.

Error Check Field Cyclical Redundancy Check (CRC)

A master’s query is comprised of a slave address (or

broadcast), a function code defining the requested action, any

data required, and an error checking field. A slave’s response is

comprised of fields confirming the action taken, any data to be

returned, and an error checking field. The query and response

both include a device address + function code + data byte(s) +

error checking field. If an error occurred in the receipt of the

query, or if the slave is unable to perform the requested action,

the slave will return an exception message as its response (see

Modbus Exceptions). The error check field allows the master to

confirm that the message contents are valid.

Modbus Message Framing

A Modbus message is placed in a frame by the transmitting

device. A frame is used to mark the beginning and ending point

of a message allowing the receiving device to determine which

device is being addressed and to know when the message is

completed. It also allows partial messages to be detected and

errors flagged as a result. RTU mode messages start with a

silent interval of at least 3.5 character times implemented as a

multiple of character times at the baud rate being used on the

network (indicated as t1t2t3t4 below). The first field transmitted

is the device address. The allowable characters transmitted for

all fields are hexadecimal values 0-9, A-F.

A networked device continuously monitors the network,

including the silent intervals, and when the first field is received

(the address), the device decodes it to determine if it is the

addressed device. Following the last character transmitted, a

similar silent interval of 3.5 character times marks the end of the

message and a new message can begin after this interval. A

typical message frame is shown below.

RTU Message Frame

Start

Addr.

Function

Data

CRC

End

t1t2t3t4 8 bits 8 bits nx8 bits 16 bits t1t2t3t4

The entire message must be transmitted as a continuous

stream. If a silent interval of more than 1.5 character times

occurs before completion of the frame, the receiving device

flushes the incomplete message and assumes the next byte will

be the address field of a new message.

In similar fashion, if a new message begins earlier than 3.5

character times following a previous message, the receiving

device assumes it is a continuation of the previous message.

This will generate an error, as the value in the final CRC field will

not be valid for the combined messages.

How Characters Are Transmitted Serially

When messages are transmitted on Modbus serial networks,

each character or byte is sent in the order of Least Significant Bit

(LSB) to Most Significant Bit (MSB) as outlined below (moving left

to right). Note that an additional stop bit is transmitted to fill out

the character frame for no parity.

RTU Character Framing (No Parity)

Start 0 1 2 3 4 5 6 7 Stop Stop

RTU Character Framing (With Parity)

Start 0 1 2 3 4 5 6 7 Parity Stop

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Modbus Addresses

The master device addresses a specific slave device by

placing the 8-bit slave address in the address field of the

message. Valid addresses are from 1-247. When the slave

responds, it places its own address in this field of its response to

let the master know which slave is responding. Address 0 is

reserved for the broadcast address, which all slave devices on a

network recognize. A slave does not issue a response to

broadcast messages. Further, not all function messages support

the broadcast address.

With respect to data addresses, all data addresses in

Modbus messages are referenced to 0, with the first occurrence

of a data item addressed as item number zero. Further, a

function code field already specifies which register group it is to

operate on (i.e. 0x, 1x, 3x, or 4x reference addresses). For

example, holding register 40001 is addressed as register 0000 in

the data address field of the message. The function code that

operates on this register specifies a “holding register” operation

and the “4xxxx” reference is implied. Holding register 40108 is

addressed as register 006BH (107 decimal).

Modbus Functions

The function code field of a message frame contains the 8

bits that tell the slave what kind of action to take. Valid codes are

in the range 1-255. Not all codes apply to a module and some

codes are reserved for future use. The following table highlights

the subset of standard Modbus functions supported by the Model

918MB-0900 module (the reference register addresses that the

function operates on are also indicated):

CODE

FUNCTION

REFERENCE

01 (01H) Read Coil (Output) Status 0xxxx

03 (03H) Read Holding Registers 4xxxx

04 (04H) Read Input Registers 3xxxx

05 (05H) Force Single Coil (Output) 0xxxx

06 (06H) Preset Single Register 4xxxx

08 (08H) Reset Slave

Hidden

15 (0FH) Force Multiple Coils (Outputs) 0xxxx

16 (10H) Preset Multiple Registers 4xxxx

17 (11H) Report Slave ID

Hidden

These functions are used to access the registers outlined in

the register map for sending and receiving data and are

described in the following paragraphs. Note that the Report

Slave ID and Reset Slave commands do not operate on register

map registers.

When a slave device responds to the master, it uses the

function code field to indicate either a normal response (error-

free), or that some kind of error has occurred (an exception

response). A normal response echoes the original function code

of the query, while an exception response returns a code that is

equivalent to the original function code with its most significant bit

(msb) set to a logic 1. For example, the Read Holding Registers

command has the function code 0000 0011 (03H). If the slave

device takes the requested action without error, it returns the

same code in its response. However, if an exception occurs, it

returns 1000 0011 (83H) in the function code field and also

appends a unique code in the data field of the response message

that tells the master device what kind of error occurred, or the

reason for the exception (See Modbus Exceptions).

The master’s application program must handle the exception

response. It may choose to post subsequent retries of the

original message, it may try sending diagnostic messages to the

slave, or it may simply notify the operator an exception error has

occurred.

The following paragraphs describe the Modbus functions

supported by the Model 918MB-0900. To gain a better

understanding of Modbus, please refer to the register map as you

review this material.

Read Coil Status (01)

This command will read the ON/OFF status of discrete

outputs or coils (0x reference addresses) in the slave. For

918MB models, its response is equivalent to reading the gate

signals of the n-channel mosfets that drive the outputs.

Broadcast transmission is not supported.

The Read Coil Status query specifies the starting coil (output

channel) and quantity of coils to be read. Coils correspond to the

discrete open-drain outputs of this transmitter and are addressed

starting from 0 (up to 4 coils addressed as 0-3 for this model).

The Read Coil Status in the response message is packed as

one coil or channel per bit of the data field. The output status is

indicated as 1 for ON (sinking current), and 0 for OFF (not

conducting). The LSB of the first data byte corresponds to the

status of the coil addressed in the query. The other coils follow

sequentially, moving toward the high order end of the byte. Since

this model has only 4 outputs, the remaining bits of the data byte

will be set to zero toward the unused high order end of the byte.

The following example reads the output channel status of

coils 0-3 at slave device 247:

Read Coil Status Example Query

Field Name

Example Value (Hex)

Slave Address 247 (F7)

Function Code 1 (01)

Starting Address High Order 0 (00)

Starting Address Low Order 0 (00)

Number Of Points High Order 0 (00)

Number Of Points Low Order 4 (04)

Error Check (CRC) --

Note that the leading character of the 0x reference address is

implied by the function code and omitted from the address

specified. In this example, the first address is 00001, referenced

via 0000H, and corresponding to coil 0.

Read Coil Status Example Response

Field Name

Example Value (Hex)

Slave Address 247 (F7)

Function Code 1 (01)

Byte Count 2 (02)

Data (Coils 3-0) 10 (0A)

Error Check (CRC) --

To summarize, the status of coils 3-0 is shown as the byte

value 0A hex, or 00001010 binary. Coil 3 is the fifth bit from the

left of this byte, and coil 0 is the LSB. The four remaining bits

(toward the high-order end) are zero. Reading left to right, the

output status of coils 3..0 is ON-OFF-ON-OFF. This is

summarized as follows:

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Bin 0 0 0 0 1 0 1 0

Hex 0 A

Coil NA NA NA NA 3 2 1 0

Read Holding Registers (03)

This command will read the binary contents of holding

registers (4x reference addresses) in the slave device. Broadcast

transmission is not supported.

The Read Holding Registers query specifies the starting

are addressed starting at 0 (registers 1-16 are addressed as 0-

15). The Read Holding Registers response message is packed

as two bytes per register, with the binary contents right-justified in

each byte. For each register, the first byte contains the high

order bits and the second byte the low order bits.

The following example reads holding registers 40007…40009

(channel 0 output value, reset value, and output configuration) at

slave device 247:

Read Holding Register Example Query

Field Name

Example Value (Hex)

Slave Address 247 (F7)

Function Code 3 (03)

Starting Address High Order 0 (00)

Starting Address Low Order 8 (08)

Number Of Points High Order 0 (00)

Number Of Points Low Order 3 (03)

Error Check (CRC) --

Read Holding Register Example Response

Field Name

Example Value (Hex)

Slave Address 247 (F7)

Function Code 3 (03)

Byte Count 6 (06)

Data High (Register 40007) (3A)

Data Low (Register 40007) 15000 (98)

Data High (Register 40008) (27)

Data Low (Register 40008) 10000 (10)

Data High (Register 40009) (00)

Data Low (Register 40009) 1 (01)

Error Check (CRC) --

To summarize, the contents of register 40007 (two bytes) is

the channel 0 output value of 15000 or 75% (3A98H). The

contents of register 40008 (two bytes) is the channel 0 reset

value of 10000 or 50% (2710H). The contents of register 40009

is the channel 0 output configuration value (two bytes) of

0-20mAV (0001H).

Note that the analog output value is expressed as a 16-bit

signed integer value with resolution of 0.005%/lsb. The range is

–163.84% (-32768 decimal) to +163.835% (+32767 decimal).

For example, -100%, 0% and +100% are represented by decimal

values –20000, 0, and 20000, respectively.

Read Input Registers (04)

This command will read the binary contents of input registers

(3x reference addresses) in the slave device. Broadcast

transmission is not supported.

The Read Input Registers query specifies the starting register

and quantity of registers to be read. Note that registers are

addressed starting at 0--registers 1-16 are addressed as 0-15.

The Read Input Registers response message is packed as

two bytes per register, with the binary contents right-justified in

each byte. For each register, the first byte contains the high

order bits and the second byte the low order bits.

The following example reads input register 30001 (module

status) at slave device 247:

Read Input Registers Example Query

Field Name

Example Value (Hex)

Slave Address 247 (F7)

Function Code 4 (04)

Starting Address High Order 0 (00)

Starting Address Low Order 2 (02)

Number Of Points High Order 0 (00)

Number Of Points Low Order 2 (02)

Error Check (CRC) --

Read Input Registers Example Response

Field Name

Example Value (

Hex)

Slave Address 247 (F7)

Function Code 4 (04)

Byte Count 6 (06)

Data High (Register 30003) 0 (00)

Data Low (Register 30003) 80 (50)

Data High (Register 30004) 0 (00)

Data Low (Register 30004) 128 (80)

Error Check (CRC) --

To summarize, the contents of register 30001 (two bytes) is

the status value of zero (0000H)--i.e. no EEPROM or flash

checksum errors present.

Force Single Coil (05)

This command will force a single coil/output (0x reference

address) ON or OFF. For broadcast transmission, this function

forces the same coil in all networked slaves.

The Force Single Coil query specifies the coil reference

address to be forced, and the state to force it to. The ON/OFF

state is indicated via a constant in the query data field. A value of

FF00H forces the coil to be turned ON (i.e. the gate of the

corresponding n-channel mosfet is set high), and 0000H forces

the coil to be turned OFF (i.e. the gate of the corresponding

output mosfet is set low). All other values are illegal and will not

affect the coil. Note that coils are referenced starting at 0—up to

4 coils are addressed as 0-3 for this model and this corresponds

to the discrete output channel number. The example below

forces discrete output 3 ON at slave device 247:

Force Single Coil Example Query

Field Name

Example Value (Hex)

Slave Address 247 (F7)

Function Code 5 (05)

Coil Address High Order 0 (00)

Coil Address Low Order 3 (03)

Force Data High Order 255 (FF)

Force Data Low Order 0 (00)

Error Check (CRC) --

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The Force Single Coil response message is an echo of the

query as shown below, returned after executing the force coil

command. No response is returned to broadcast queries from a

master device.

Force Single Coil Example Response

Field Name

Example Value (Hex)

Slave Address 247 (F7)

Function Code 5 (05)

Coil Address High Order 0 (00)

Coil Address Low Order 3 (03)

Force Data High Order 255 (FF)

Force Data Low Order 0 (00)

Error Check (CRC) --

Preset Single Register (06)

This command will preset a single holding register (4x

reference addresses) to a specific value. Broadcast transmission

is supported by this command and will act to preset the same

The Preset Single Register query specifies the register

reference address to be preset, and the preset value. Note that

registers are addressed starting at 0--registers 1-16 are

addressed as 0-15. The Preset Single Registers response

message is an echo of the query, returned after the register

contents have been preset. The following example writes a baud

rate of 9600bps to holding register 40002 (Baud Rate) at slave

device 247:

Preset Holding Register Example Query

Field Name

Example Value (Hex)

Slave Address 247 (F7)

Function Code 6 (06)

Preset Data High Order 0 (00)

Preset Data Low Order 2 (02)

Error Check (CRC) --

Preset Holding Register Example Response

Field Name

Example Value (Hex)

Slave Address 247 (F7)

Function Code 6 (06)

Preset Data High Order 0 (00)

Preset Data Low Order 2 (02)

Error Check (CRC) --

The response simply echoes the query after the register

contents have been preset. No response is returned to broadcast

queries from a master device.

Force Multiple Coils (15)

This command will simultaneously force a sequence of coils

(0x reference addresses) either ON or OFF. Broadcast

transmission is supported by this command and will act to force

the same block of coils in all networked slaves.

The Force Multiple Coils query specifies the starting coil

reference address to be forced, the number of coils, and the force

data to be written in ascending order.

The ON/OFF states are specified by the contents in the query

data field. A logic 1 in a bit position of this field requests that the

coil turn ON, while a logic 0 requests that the corresponding coil

be turned OFF. Unused bits in a data byte should be set to zero.

Note that coils are referenced starting at 0—up to 4 coils are

addressed as 0-3 for this model and this also corresponds to the

discrete output channel number.

The Force Multiple Coils normal response message returns

the slave address, function code, starting address, and the

number of coils forced, after executing the force instruction. Note

that it does not return the byte count or force value. The following

example forces outputs 1 & 3 OFF, and 0 & 2 ON for coils 0-3 at

slave device 247:

Force Multiple Coils Example Query

Field Name

Example Value (He

Slave Address 247 (F7)

Function Code 15 (0F)

Coil Address High Order 0 (00)

Coil Address Low Order 0 (00)

Number Of Coils High Order 0 (00)

Number Of Coils Low Order 4 (04)

Byte Count 01

Force Data High (First Byte) 5 (05)

Error Check (CRC) --

Note that the leading character of the 0x reference address is

implied by the function code and omitted from the address

specified. In this example, the first address is 00001

corresponding to coil 0 and referenced via 0000H. Thus, the data

byte transmitted will address coils 3...0, with the least significant

bit addressing the lowest coil in this set as follows (note that the

four unused upper bits of the data byte are set to zero):

Bin

Hex

Coil

Force Multiple Coils Example Response

Field Name

Example Value (Hex)

Slave Address 247 (F7)

Function Code 15 (0F)

Coil Address High Order 0 (00)

Coil Address Low Order 0 (00)

Number Of Coils High Order 0 (00)

Number Of Coils Low Order 4 (04)

Error Check (CRC) --

The normal response returns the slave address, function

code, starting coil address, and quantity of coils forced, after

executing the force instruction. It does not return the byte count

or force data. No response is returned to broadcast queries from

a master device.

Preset Multiple Registers (16)

This command will preset a block of holding registers (4x

reference addresses) to specific values. Broadcast transmission

is supported by this command and will act to preset the same

block of registers in all networked slaves.

The Preset Multiple Registers query specifies the starting

to be written in ascending order.

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Note that registers are addressed starting at 0--registers 1-16 are

addressed as 0-15. The Preset Multiple Registers normal

response message returns the slave address, function code,

starting register reference, and the number of registers preset,

after the register contents have been preset. Note that it does

not echo the preset values.

The following example writes a new slave address of 200, a

baud rate of 28800bps, and sets parity to even, by writing to

holding registers 40001 through 40003 at slave device 247

(changes to slave address, baud rate, and parity will take effect

following the next software or power-on reset):

Preset Multiple Registers Example Query

Field Name

Example Value (Hex)

Slave Address 247 (F7)

Function Code 16 (10)

Starting Register High Order 0 (00)

Starting Register Low Order 0 (00)

Number Of Registers High Order 0 (00)

Number Of Registers Low Order 3 (03)

Byte Count 6 (06)

Preset Data High (First Register) 0 (00)

Preset Data Low (First Register) 200 (C8)

Preset Data High (Second Reg) 0 (00)

Preset Data Low (Second Reg) 5 (05)

Preset Data High (Third Reg) 0 (00)

Preset Data Low (Third Reg) 2 (02)

Error Check (CRC) --

Preset Multiple Registers Example Response

Field Name

Example Value (Hex)

Slave Address 247 (F7)

Function Code 16 (10)

Starting Register High Order 0 (00)

Starting Register Low Order 0 (00)

Number Of Registers High Order 0 (00)

Number Of Registers Low Order 3 (03)

Error Check (CRC) --

The response simply echoes the query without returning the

preset values after the register contents have been preset. No

response is returned to broadcast queries from a master device.

Report Slave ID (17)

This command returns the model number, serial number, and

firmware number for the Acromag slave device, the status of the

Run indicator, and any other information specific to the device.

This command does not address Register Map registers.

Broadcast transmission is not supported.

The Report Slave ID query simply sends the slave address

and function code with error check (CRC) as follows:

Report Slave ID Example Query

Fiel

d Name

Example Value (Hex)

Slave Address 247 (F7)

Function Code 17 (11)

Error Check (CRC) --

Report Slave ID Sample Response

Field Name

Example Value (Hex)

Slave Address 247 (F7)

Function Code 17 (11)

Byte Count 26 (1A)

Acromag Slave ID

0 (00H) = 924MB-0900

1 (01H) = 913MB-0900

2 (02H) = 914MB-0900

3 (03H) = 917MB-0900

4 (04H) = 918MB-0900

5 (05H) = 901MB-0900

6 (06H) = 902MB-0900

7 (07H) = 903MB-0900

8 (08H) = 904MB-0900

9 (09H) = 905MB-0900

10 (0AH) = 906MB-0900

Run Indicator Status (ON) 255 (FF)

Firmware Number ASCII

Byte String (Additional

Data Field)

“ACROMAG, 9300-037A,

917MB-0900,”

(41 43 52 4F 4D 41 47 2C 39 33

30 30 2D 30 33 37 41 2C 39 31

37 4D 42 2D 30 39 30 30 2CH)

Serial Number ASCII Byte

String (Unique Per Module)

Six Numbers + Revision

“123456A”

(31 32 33 34 35 36 41H)

Error Check (LRC or CRC) --

Reset Slave (08)

This command is used to trigger a reset of the module and its

effect is equivalent to a power-on reset of the module. Note that

changes to baud rate, slave address, and parity are initiated

following reset. The Reset Slave command uses sub-function 01

(Restart Communications) of the standard Modbus Diagnostics

Command (08) to accomplish a module reset. This function does

not operate on register map locations. Broadcast transmission is

not supported.

The Reset Slave query simply sends the slave address,

function code, sub-function code, and data (data is ignored and

simply echoed back), with error check (CRC). A Reset Slave

response is simply an echoed acknowledge that is returned just

before the reset is executed. Allow a few seconds following reset

to re-initiate communication with a module.

Reset Slave Example Query

Field Name

Example Value (Hex)

Slave Address 247 (F7)

Function Code 08 (08)

Sub-Function High Order Byte 0 (00)

Sub-Function Low Order Byte 1 (01)

Data Field High-Order Byte 0 (00)

Data Field Low Order Byte 0 (00)

Error Check (CRC) --

Reset Slave Example Response (Sent Prior To Reset)

Field Name

Example Value (Hex)

Slave Address 247 (F7)

Function Code 08 (08)

Sub-Function High Order Byte 0 (00)

Sub-Function Low Order Byte 1 (01)

Data Field High-Order Byte 0 (00)

Data Field Low Order Byte 0 (00)

Error Check (CRC) --

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Note that the response simply echoes the query just before

the reset is triggered.

For Modbus software that does not support the Reset Slave

function, an alternate method of generating a module reset is

provided via a write to the Calibration Access & Module Reset

Modbus Data Field

The data field of a message frame contains a multiple of 8

bits that provides the slave with any additional information the

slave requires to complete the action specified by the function

code. The data field typically includes register addresses, count

values, and written data. The data field can be nonexistent for

some commands (zero length), as not all messages require data.

If no error occurs, the data field of a response from a slave

will return the requested data. If an error occurs, the data field

returns an exception code (see Modbus Exceptions) that the

master application can use to determine the next action to take.

Supported Data Types

All I/O values are accessed via 16-bit Input Registers or 16-

bit Holding Registers (see Register Map). Input registers contain

information that is read-only. For example, the current input

value read from a channel, or the states of a group of digital

inputs. Holding registers contain read/write information that may

be configuration data or output data. For example, the high limit

value of an alarm function operating at an input, or an output

value for an output channel. I/O values for this model are

represented by the following simple data types for percent-of-

span, and discrete on/off.

Summary Of Data Types Used By 900MB Modules

Data Types

Description

Count Value A 16-bit signed integer value representing

an A/D count, a DAC count, or a time value

with a range of –32768 to +32767.

Percentage A 16-bit signed integer value with resolution

of 0.005%/lsb. ±20000 is used to represent

±100%. For example, -100%, 0% and

+100% are represented by decimal values

–20000, 0, and 20000, respectively. The

full range is –163.84% (-32768 decimal) to

+163.835% (+32767 decimal).

Temperature A 16-bit signed integer value with resolution

of 0.1°C/lsb. For example, a value of

12059 is equivalent to 1205.9°C, a value of

–187 equals –18.7°C. The maximum

possible temperature range is –3276.8°C to

+3276.7°C.

Discrete A discrete value is generally indicated by a

single bit of a 16-bit word. The bit

number/position typically corresponds to

the discrete channel number for this model.

Unless otherwise defined for outputs, a 1

bit means the corresponding output is

closed or ON, a 0 bit means the output is

open or OFF. For inputs, a value of 1

means the input is in its high state (usually

>> 0V), while a value of 0 specifies the

input is in its low state (near 0V).

Modbus Error Checking Fields

Modbus networks employ two methods of error checking:

parity checking (even or odd parity, or none), and frame checking

(Cyclical Redundancy Check).

Parity Checking

A Modbus device can be configured for Even or Odd parity

checking, or for no parity checking, and this determines how the

parity bit of the data frame is set.

If even or odd parity checking is selected, the number of 1

bits in the data portion of each character frame is counted. Each

character in RTU mode contains 8 bits. The parity bit will then be

set to a 0 or a 1, to result in an even (Even parity), or odd (Odd

parity) total number of 1 bits.

For example, if an RTU character frame contains the

following eight data bits: 1100 0011, then since the total number

of 1 bits is 4 (already an even number), the frame’s parity bit will

be 0 if even parity is selected. If odd parity is used, then the

parity bit will be set to 1, making the total number of one bits an

odd number (five).

When a message is transmitted, the parity bit is calculated

and applied to the frame of each character transmitted. The

receiving device counts the quantity of 1 bits in the data portion of

the frame and sets an error flag if the count differs from that sent.

As such, parity checking can only detect an error if an odd

number of bits are picked up or dropped off from a character

frame during transmission. For example, if odd parity is

employed and two 1 bits are dropped from a character, the result

is still an odd count of 1 bits. Note that all devices on a Modbus

network must use the same parity.

If no parity checking is selected, then no parity bit is

transmitted and no parity check is made. An additional stop bit is

transmitted to fill out the character frame for the no parity

selection. The Acromag device will actually work with 1 or 2 stop

bits with no parity selected.

CRC Error Checking

RTU Mode message frames include an error checking

method that is based on a Cyclical Redundancy Check (CRC).

The error checking field of a frame contains a 16-bit value (two 8-

bit bytes) that contain the result of a Cyclical Redundancy Check

(CRC) calculation performed on the message contents.

The CRC value is calculated by the transmitting device and is

appended to the message as the last field in a message—the low

order byte is appended first, followed by the high-order byte.

Thus, the CRC high-order byte is the last byte to be sent in a

message. The receiving device calculates a CRC during receipt

of a message and compares the calculated value to that received

in the CRC field. If the two values differ, an error results.

The CRC is started by first preloading the 16-bit CRC register

to all 1’s. Successive 8-bit bytes of the message (only the 8-data

bits in each character--no start, stop, or parity bits) are applied to

the current contents of the register, and each 8-bit character is

exclusive OR’ed with the register contents.

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The exclusive OR result is shifted in the direction of the least

significant bit (lsb) of the CRC, with a zero placed into the most

significant bit (msb). The lsb is then extracted and examined, if

the lsb is a 1, the register is exclusive OR’ed with a preset fixed

value. If the lsb is a 0, no exclusive OR takes place. This

process is repeated until 8 shifts have been performed. After the

last (eighth) shift, the next 8-bit byte is exclusive OR’ed with the

more shifts as described above. The final contents of the CRC

CRC value.

Modbus Exceptions

If an unsupported function code is sent to a module, then the

exception code 01 (Illegal Function) will be returned in the data

field of the response message. If a holding register is written with

an invalid value, then exception code 03 (Illegal Data Value) will

be returned in the response message. The following table lists

the possible exception codes:

Modbus Exception Codes

Code Exception Description

01 Illegal

Function

The function code received in the

query is not allowed or invalid.

02 Illegal Data

Address

The data address received in the

query is not an allowable address for

the slave or is invalid.

03 Illegal Data

Value

A value contained in the query data

field is not an allowable value for the

slave or is invalid.

04 Slave Device

Failure

An unrecoverable error occurred

while the slave was attempting to

perform the requested action.

05 Acknowledge The slave has accepted the request

and is processing it, but a long time

is required to do so. This response

is used to prevent a timeout error

from occurring in the master.

06 Slave Device

Busy

The slave is engaged in processing a

long-duration program command.

The master should retransmit the

message later when the slave is free.

08 Memory

Parity Error

The slave attempted to read

extended memory, but detected a

parity error in memory. The master

can retry the request, but service

may be required at the slave device.

07 Negative

Acknowledge

The slave cannot perform the

function received in the query. This

code is returned for an unsuccessful

programming request using function

code 13 or 14 (codes not supported

by this model). The master should

request diagnostic info from the

slave.

In a normal response, the slave echoes the function code of

the original query in the function field of the response. All

function codes have their most-significant bit (msb) set to 0 (their

values are below 80H).

In an exception response, the slave sets the msb of the

function code to 1 in the returned response (i.e. exactly 80H

higher than normal) and returns the exception code in the data

field. This is used by the master’s application to recognize an

exception response and direct an examination of the data field for

the applicable exception code.

MODULE SOFTWARE CONFIGURATION

As shipped from the factory, each module has a default

configuration as detailed in the INSTALLATION section of this

manual. Your application will likely differ from the default

configuration and the module will need to be reconfigured. Series

900MB modules may be easily configured and calibrated by

simply issuing the appropriate Modbus functions to the Register

Map registers, as required to configure the unit. However, it is

much simpler to use the controls of the 900MB Configuration

Software to program and control the Model 918MB-0900

transmitter parameters and operating modes. This software is

generally easy to use and self explanatory. Complete

configuration only takes a few minutes. On-line help is also built-

in and includes context sensitive help. As such, a

comprehensive guide to the use of this program is not necessary.

However, to begin configuration, you should already be familiar

with Windows operation and have a basic understanding of

transmitter terminology as it relates to this model.

Before You Begin

1. Have you installed the 900MB Configuration Program? You

should complete the MODULE INSTALLATION section

(Section 2.0) of this manual before proceeding.

2. Check that all necessary electrical connections have been

made and that power is applied (module’s green LED ON).

3. Have you set the correct baud rate at the RS485 converter

(or repeater if used)?

4. Have you tried communicating using the Default

Communication Mode? Press the “DFT” push-button of the

918MB module until the yellow status LED is flashing. This

sets the module’s communication parameters to 9600 baud,

a slave address of 247, no parity, and two stop bits. Be sure

to also set the baud rate of the RS485 converter or network

repeater to 9600 baud.

5. If you fail to communicate with the module or have a high

degree of communication errors, try increasing the response

delay time (See Response Delay Register 40010). Some

network converters or host/software systems cannot accept

an immediate response from a slave device without

additional delay.

The following sections guide you through the 900MB

Configuration Program property sheets used to configure the

918MB Transmitter. These sheets vary slightly between models,

but the general approach is the similar. Refer to on-line Help if

you have trouble understanding parameters unique to your

module.

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Starting The Program

After clicking on the Series 900MB

program icon to boot the Configuration

Program, a screen similar to the one at

right will be displayed. To begin, click

the “Settings-Serial Communications…”

pull-down menu (or press Ctrl-E) to set

the COM port, baud rate, parity, and

slave address that the host computer

will use to communicate with the

module (as shown at right). Optionally,

you can check the “Update

Communications settings at download”

box to automatically change the host

settings to match the module if new

settings are later downloaded to the

module (recommended to conveniently

maintain communication with a module

following reconfiguration).

↑↑

Available menu selections are listed below. COM Port MODULE

Note that the host COM port

selected is indicated in the first

box of the lower right-hand

corner. MODULE is indicated in

the third box if a connected

module is detected by the

software. The fourth and fifth

boxes indicate NUM lock and

CAP’s lock, respectively.

File

New…

Open…

Save

Save As…

Print…

Print Preview

Print Setup…

Recent File Indicated

Exit

Use File-New to create a new

configuration file. You will be

prompted to select a model

number. Use File-Open to open

an existing configuration file.

Use File-Save to save the

current configuration file to disk.

Use File-Save As to save the

current configuration file to a new

file name.

Use File-Print to get a printout of

the currently loaded configuration

file.

Use File-Print Preview to view

the current configuration or

preview the print documentation.

Use File-Print Setup to select a

printer and font style.

Module

Upload Configuration

Download Configuration

Use Module-Upload

Configuration to upload the

module’s current configuration

and calibration.

Use Module-Download

Configuration to write the

currently loaded configuration to

the module.

Settings-

Serial Communications…

Communications Port

Host Baud Rate

Host Parity

Slave Address

Use the Communications Port

scroll window to select the host

COM port the module is

connected to (COM1-COM4), or

type in a COM port as required,

from COM1 to COM99. The

selected COM port is indicated in

the lower right hand corner of the

screen.

Use the Baud Rate scroll window

to select the baud rate to be used

by the host in communicating

with the module.

Use the Parity scroll window to

select Odd, Even, or No Parity

checking by the software for data

transfer.

Use the Slave Address scroll

window to tell the software which

module to address.

If you wish to maintain

communications with a module

following download, you should

check the “Update

Communications settings at

download” box of the Settings

window to keep the host in synch

with a module if the module

settings are changed.

If the module is in the Default

Mode (indicated via a flashing

status LED), the baud rate,

address, and parity assumed by

the module are fixed at 9600bps,

247, and No Parity. You must

use the same settings as the

connected module.

Help

Configuration Help Topics

Your Model Help Topics

About Modbus Configuration

About Your Model

Use Help to obtain information

about using this software or

configuring transmitters. Note

that context sensitive help (↑?) is

also available for help on a

specific field or topic. Simply

click on the [↑?] button, then click

on the field or topic of interest to

obtain help on that subject. You

may also click the right mouse

button to copy or print the help

screen while it is being displayed.

The following sections review the

configuration of a Model

918MB-0900 transmitter module.

Configuration of your model will

be similar.

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Creating A Configuration File

You may use File-New to create a new

configuration file, or File-Open to open

an existing configuration file. You may

also use Module-Upload

Configuration to retrieve the current

active configuration from the module

connected (recommended).

Uploading first is recommended as it will

automatically detect the correct model

connected and load the property sheets

for that model.

Once you create, open, or upload a

configuration file, a screen similar to the

one shown at right will be displayed.

The model number is indicated at the

top of the screen along with the current

file name. The Model 917MB-0900

Configuration screen is shown here.

Your screen will vary according to your

model number.

Note that 3 property sheets define this

transmitter’s configuration: General,

Test, and Output Calibration.

Module

The Serial and Firmware numbers

indicated at the top of the General

screen cannot be modified.

For “Tag:”, enter up to 15 alphanumeric

characters (optional).

For “Comment:”, enter up to 31

alphanumeric characters (optional).

For “Configured By:”, enter your name

up to 15 alphanumeric characters

(optional).

You can also add a “Location:” note of

up to 25 alphanumeric characters

(optional).

For “Channel ID:”, enter up to 15

alphanumeric characters of

identification information relative to the

output channel (optional).

Use the “Slave Address” scroll bar to

select a new module address that will

take effect following download. Select

from 1 to 247. Address 247 is reserved

for Default Mode.

Use the “Baud Rate” scroll bar to

select a new baud rate to be used by

the module following download. Select

2400, 4800, 9600 (Default Mode),

14400, 19200, 28800, 38400, 57600,

76800, or 115200 bits per second.

Use the “Parity” scroll bar to select

Odd, Even, or No Parity (Default Mode)

error checking by the module.

Use the “Response Delay” field to

specify a delay from 0 to 65500 ticks

with 1 tick equal to 1.085 micro-

seconds. Response delay is the

additional turnaround delay applied

between message receipt by the

module and its response to the host. A

fixed amount of delay is already present

and varies with the model. Thus, you

will have to specify a comparable

amount of response delay to measure

any affect. Some host software or

signal converters require additional

delay to work properly.

Note that slave address, baud rate, and

parity selections take effect following a

configuration download and do not alter

the settings used by the host software

(which are configured separately via the

Settings menu).

If you checked the “Update

Communications Settings at Download”

box of the Settings pull-down menu, this

software will change the host settings to

match the module settings that take

effect following a download in an effort

to maintain communication with the

module. Otherwise, you must change

the host Settings separately after

downloading to match the new module

settings.

If the module is in Default Mode

(indicated via a flashing status LED),

the baud rate, address, and parity of the

module are fixed at 9600bps, 247, and

No Parity.

Output (All Channels)

Use the “Range:” scroll bar to pick one

of the following ranges according to

your model:

917MB: 918MB:

0-20mA 0-10V DC

4-20mA 0-5V DC

0-1mA 0-1V DC

The analog output utilizes percent-of-

span units with ±20000 representing

±100%. That is, for the 4-20mA range,

a 0% indication (0) represents 4mA and

100% (20000) represents 20mA.

Available ranges will vary according to

your model number. All output ranges

have been factory calibrated. To begin

configuring your module, start by

selecting an output range as required.

Use the “Watchdog Time:” field to

specify a watchdog period up to 65534

seconds (18.2 hours). 0 or 65535 will

disable the watchdog function.

Check the “Watchdog Reset” box to

optionally set the output channels to

specific states or levels following a

watchdog timeout (see following page).

The next section covers Watchdog

Timeout Value Configuration for the

output channels of this model. Note

that you can only make changes to the

parameters of the following page if you

have configured a Watchdog Timeout

delay and checked the Watchdog Reset

box as described above.

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Watchdog Timeout States/Values

Click on the “Watchdog Timeout State 0

& 1”, or “Watchdog Timeout State 2 &

3” property sheet tabs and a screen

similar to the one at right will be

displayed. The Model 917MB-0900

watchdog screen is shown here (Model

918MB-0900 screen is similar).

If you checked the “Watchdog Reset”

box of the General property sheet

described on the previous page, you will

be allowed to make changes to the

parameters of this page.

Use this page to configure the watchdog

timeout output states and levels for the

corresponding digital and analog

outputs. Timeout states and levels may

be set for each of the four analog and

digital outputs of this model. A

watchdog timeout will automatically

drive the outputs to the states/levels

defined here when enabled.

A watchdog timer may be applied to the

output channels of this module and the

timeout delay is set via the General

property sheet (described on the

previous page). A watchdog timeout will

occur if no channel I/O has occurred

over the specified timeout period. For

example, if communication with the unit

is lost. Optionally, you can use the

parameters of this property sheet to

define the states that the digital outputs

are to be programmed to upon output

timeout. You can also define the

timeout levels that the analog outputs

will be programmed to upon timeout.

Watchdog timeout state or level control

takes precedence over direct control of

the output channels. A watchdog

timeout is cleared and the timer

reinitiated via a read or write to any

output channel, or by resetting the

module. Note that clearing a timeout

does not set the outputs to their pre-

timeout state--they remain in their

timeout state until otherwise written.

Before you can make changes to output

timeout states or levels, you must have

already configured a watchdog timeout

value and have checked the “Watchdog

Reset” box of the General property

sheet as described on the previous

page.

Use the “Digital Output Watchdog

Timeout Value” scroll bar to select On

or Off for the corresponding digital

output channel. This defines the state

the corresponding output will be

programmed to following a watchdog

timeout. After a timeout is cleared, the

output remains in its current state until

otherwise written.

Note that the digital output channels of

this module are open-drain mosfet (low-

side) switches. On refers to an output

that is sinking current. Off refers to a

switch that is not conducting.

Use the channel “Analog Output

Watchdog Timeout Value” field to

define the level the analog output is to

assume following a watchdog timeout.

If you check the “No Change” check box

just below this field, the analog output

will not be affected by a watchdog

timeout. Note that after a timeout is

cleared, the output remains at the

current level until otherwise written.

Note that the analog output channels

utilize percent-of-span units with ±20000

representing ±100%. That is, for the 4-

20mA range, a 0% indication (0)

represents 4mA (or 0mA for 0-20mA

range), and 100% (20000) represents

20mA. You can enter a value from 0 to

20500 for the Model 917MB.

The “Watchdog Timeout State 2 & 3”

property sheet is configured in the same

fashion, but applied to outputs 2 and 3.

The next section covers testing of your

module. Use the Test page to check

output operation and/or monitor output

states and levels.

BusWorksModel 917MB/918MB Network I/O Module User’s Manual Quad Current/Voltage Output

___________________________________________________________________________________________

- 19 -

Testing Your Configuration

The “Test” portion of this program

allows you to monitor polling, monitor

module status flags, restore factory

calibration, reset the module, monitor

output ranges and values, and control or

monitor output levels and states.

Test Operation

Click on the “Test” property sheet tab to

test the configuration just written to your

module and a screen similar to the one

at the right will be displayed (Model

917MB-0900 Test screen shown).

The flashing green Status lamp next to

“Polling Status” indicates the software is

communicating with the module and

polling its I/O. Polling is automatic

when this screen is displayed and turns

off if another screen is selected.

The graphic simulation of the module

LED’s reflects the current LED status of

the module.

You can reset the module by clicking

the “Reset” button (same effect as

power-on reset). Note that a module

will exit the Default Mode following a

reset. New address, baud rate, and

parity settings will take effect

immediately following a reset—to

continue communications following

reset, be sure to make host software

adjustments accordingly via the Settings

pull-down menu.

For each analog output, the current

selected output range and output value

(“Value:”) are indicated. A type field and

Write button are provided for writing the

output count. The count value is written

in percent-of-span units with ±20000

representing ±100%. You can write any

value from 0 to 20500 for the Model

917MB-0900. That is, for the 4-20mA

output range selection, enter 0 for a 0%

(4mA) output value, or 20000 for a

100% (20mA) output value.

NOTE: The module always uses

percent-of-span units as described

above. Translation to milliamp (mA)

indication in the “Value:” field is done via

this software. Keep this in mind when

using other software packages to read

or write values to a module. Note also

that “Value:” is computed via this

software and may not represent the

actual output reading (it is not a read

value).

If polling is OFF, then the last

transmitted values are indicated. If the

module is not connected or powered,

then an “Unable to communicate with

module” message is displayed.

You can write a value to the output by

typing a percent-of-span value into the

corresponding field box and then

clicking on the adjacent “Write” button.

Click buttons are also provided for each

digital output. Click the “On” button to

turn the output ON (sinking current), or

click the “Off” button to turn it OFF

(open). The actual state of the output is

indicated in the Digital Output States

section on the left side of the screen.

The current state is also indicated via

the yellow Digital Output LED’s of the

module graphics.

If you miscalibrate a module, or your

calibration appears in error, you can use

the “Restore Default Calibration” button

to restore a module’s original factory

output calibration (all outputs are

restored together).

Print Your Configuration

If you wish to document your transmitter

configuration, then select File-Print to

get a two page printout of all of your

selected configuration parameters.

Saving Your Configuration

You should select File-Save As to save

your configuration file to disk and give it

a new file name.

Use File-Save to save the current file

without renaming it.

Note that the currently loaded

configuration file name is indicated at

the top of the screen to the right of the

model number.

In the event that you lose a

configuration file, you can always

upload it from the module via Module-

Upload Configuration.

Note that the configuration process may

vary slightly for other model types.

Now wasn’t that easy! That’s all there is

to using the configuration software to

configure your module. The module is

now ready for installation in the field.

The next section covers output

calibration of your module. Note that

calibration has already been done at the

factory and readjustment is not

generally required. However, periodic

recalibration may be performed to

correct for component aging, or as part

of your company’s maintenance

requirements.

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