GE P485 User manual

GE Multilin
215 Anderson Avenue, Markham, Ontario
Canada L6E 1B3
Tel: [phone] Fax: [phone]
Internet: http://www.GEmultilin.com
P485 Modbus to Profibus
Converter
Instruction Manual
Manual P/N: 1601-0237-A1
Manual Order Code: GEK-113190
Copyright © 2005 GE Multilin
ISO9001:2000
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GE Multilin's Quality
Management System is
registered to ISO9001:2000
QMI # 005094
UL # A3775
GE Consumer & Industrial

P485 MODBUS TO PROFIBUS CONVERTER – USER GUIDE i
GE Consumer & Industrial
P485 Modbus to Profibus
Converter
Table of contents
INTRODUCTION Getting started........................................................................................................1–1
Inspecting the package and product.................................................................................................1–1
Contact information...................................................................................................................................1–1
Document conventions..........................................................................................1–2
Description .....................................................................................................................................................1–2
Glossary...........................................................................................................................................................1–2
About the P485 Modbus to Profibus Converter.................................................1–3
Application......................................................................................................................................................1–3
Features....................................................................................................................1–3
General features..........................................................................................................................................1–3
Modbus network..........................................................................................................................................1–3
Fieldbus interface features.....................................................................................................................1–3
Ordering ...................................................................................................................1–4
Order codes....................................................................................................................................................1–4
Specifications ..........................................................................................................1–4
Mechanical .....................................................................................................................................................1–4
Electrical characteristics..........................................................................................................................1–4
Communications .........................................................................................................................................1–4
Environmental...............................................................................................................................................1–4
EMC compliance ..........................................................................................................................................1–4
INSTALLATION Quick install .............................................................................................................2–1
Procedure........................................................................................................................................................2–1
Electrical installation .............................................................................................2–1
Overview..........................................................................................................................................................2–1
Profibus connector .....................................................................................................................................2–2
Configuration cable....................................................................................................................................2–3
Modbus connector......................................................................................................................................2–4
Power connector .........................................................................................................................................2–4
Mechanical installation .........................................................................................2–5
DIN-rail mounting........................................................................................................................................2–5
Indicators and switches ........................................................................................2–5
Status indicators..........................................................................................................................................2–5
Configuration switches.............................................................................................................................2–6

ii P485 MODBUS TO PROFIBUS CONVERTER – USER GUIDE
TABLE OF CONTENTS
Profibus installation procedure ...........................................................................2–7
Profibus configuration tool.....................................................................................................................2–7
Profibus network termination ...............................................................................................................2–7
Links ..................................................................................................................................................................2–7
Troubleshooting......................................................................................................2–8
dESCRIPTION .................................................................................................................................................2–8
DATA EXCHANGE Overview...................................................................................................................3–1
Description.....................................................................................................................................................3–1
Internal memory buffer structure.......................................................................................................3–1
Memory Map............................................................................................................3–2
Memory locations.......................................................................................................................................3–2
Protocol configuration...........................................................................................3–3
Description.....................................................................................................................................................3–3
Communication mode.............................................................................................................................. 3–3
Protocol building blocks........................................................................................................................... 3–3
SOFTWARE
OVERVIEW
Introduction .............................................................................................................4–1
Description.....................................................................................................................................................4–1
System requirements................................................................................................................................4–1
Installation procedure ...........................................................................................4–1
Description.....................................................................................................................................................4–1
Installing from EnerVista CD.................................................................................................................. 4–1
Installing from the GE Multilin website..............................................................................................4–1
Using the EnerVista P485/D485 Setup software ...............................................4–2
Description.....................................................................................................................................................4–2
Configuration wizard.................................................................................................................................4–2
Select fieldbus type....................................................................................................................................4–3
Sub-network properties ........................................................................................................................... 4–4
Device types..................................................................................................................................................4–5
Connecting devices.................................................................................................................................... 4–7
Selecting parameters for each node.................................................................................................4–8
Configuration report.................................................................................................................................. 4–8
Configuration main window .................................................................................4–9
Description.....................................................................................................................................................4–9
Navigation window ................................................................................................................................. 4–10
Parameter window.................................................................................................................................. 4–10
Information window ............................................................................................................................... 4–10
Configuration line indicator ................................................................................................................ 4–10
Options window........................................................................................................................................ 4–11
Fieldbus configuration ........................................................................................ 4–11
Description.................................................................................................................................................. 4–11
P485/D485 configuration ................................................................................... 4–12
Parameter window.................................................................................................................................. 4–12
Modbus network configuration......................................................................... 4–13
Overview ...................................................................................................................................................... 4–13
Serial interface settings ........................................................................................................................ 4–13
COMMUNICATION
MODEL
Introduction .............................................................................................................5–1
Description.....................................................................................................................................................5–1
Scan list............................................................................................................................................................5–2

TABLE OF CONTENTS
P485 MODBUS TO PROFIBUS CONVERTER – USER GUIDE iii
Basic settings ..........................................................................................................5–2
Parameter window .....................................................................................................................................5–2
Communication............................................................................................................................................5–2
Message delimiter.......................................................................................................................................5–2
Nodes ........................................................................................................................5–3
Description .....................................................................................................................................................5–3
Node parameters ........................................................................................................................................5–3
Modbus network menu.............................................................................................................................5–3
Node menu.....................................................................................................................................................5–3
Query parameters ......................................................................................................................................5–4
Response parameters...............................................................................................................................5–5
FRAME AND
COMMAND EDITORS
Frame editor ............................................................................................................6–1
Description .....................................................................................................................................................6–1
Example ...........................................................................................................................................................6–1
Command editor .....................................................................................................6–2
General.............................................................................................................................................................6–2
Specifying a new command ..................................................................................................................6–3
MODBUS NETWORK
AND NODE
MONITORS
Modbus network monitor......................................................................................7–1
General.............................................................................................................................................................7–1
Operation ........................................................................................................................................................7–2
Node monitor...........................................................................................................7–3
General.............................................................................................................................................................7–3
Operation ........................................................................................................................................................7–3
ADVANCED
FUNCTIONS
Control and status registers.................................................................................8–1
Description .....................................................................................................................................................8–1
Control register (Profibus control system to P485)......................................................................8–1
Control codes ................................................................................................................................................8–2
Status register (P485 to fieldbus control system).........................................................................8–2
Status codes ..................................................................................................................................................8–3
Handshaking procedure ..........................................................................................................................8–3
Input/output data during startup .......................................................................8–4
Description .....................................................................................................................................................8–4
Advanced fieldbus configuration.........................................................................8–5
Mailbox command......................................................................................................................................8–5
APPLICATION
EXAMPLE
Introduction.............................................................................................................9–1
Overview..........................................................................................................................................................9–1
Equipment and documents....................................................................................................................9–1
System setup.................................................................................................................................................9–2
Modbus user map setup ........................................................................................9–3
Description .....................................................................................................................................................9–3
PQMII user map............................................................................................................................................9–3
MM2 user map..............................................................................................................................................9–3
System configuration.............................................................................................9–5
Overview..........................................................................................................................................................9–5
Installing the Enervista P485/D485 Setup software ...................................................................9–6
Starting the configuration wizard........................................................................................................9–6

iv P485 MODBUS TO PROFIBUS CONVERTER – USER GUIDE
TABLE OF CONTENTS
Step 1: Selecting the fieldbus type...................................................................................................... 9–6
Step 2: Selecting the sub-network properties ...............................................................................9–7
Step 3: Include device types ..................................................................................................................9–7
Step 4: Connect devices to the sub-network.................................................................................9–9
Step 5: Select parameters for each node..................................................................................... 9–10
Step 6: Configuration report ............................................................................................................... 9–11
Saving device data.................................................................................................................................. 9–12
Configuring the queries......................................................................................................................... 9–12
Downloading the configuration file................................................................................................. 9–15
Profibus network setup....................................................................................... 9–16
Description.................................................................................................................................................. 9–16
MISCELLANEOUS Revision history.................................................................................................... 10–1
Release dates............................................................................................................................................. 10–1
Changes to the manual ........................................................................................................................ 10–1
Warranty............................................................................................................... 10–1
GE Multilin warranty statement........................................................................................................ 10–1

P485 MODBUS TO PROFIBUS CONVERTER – USER GUIDE 1–1
GE Consumer & Industrial
P485 Modbus to Profibus
Converter
Chapter 1: Introduction
Introduction
Getting started
INSPECTING THE
PACKAGE AND PRODUCT
Examine the shipping container for obvious damage prior to installing this product; notify
the carrier of any damage that you believe occurred during shipment or delivery. Inspect
the contents of this package for any signs of damage and ensure that the items listed
below are included.
Remove the items from the shipping container. Be sure to keep the shipping container
should you need to re-ship the unit at a later date.
In the event there are items missing or damaged, contact the party from whom you
purchased the product. If the unit needs to be returned, please use the original shipping
container, if possible.
CONTACT INFORMATION GE Multilin contact information and call center for product support is shown below:
GE Multilin
215 Anderson Avenue
Markham, Ontario
Canada L6E 1B3
• Telephone: [phone] or 1-800-547-8629 (North America),
[phone] (Europe)
Fax: [phone] (North America),
[phone] (Europe)
• E-mail: [email protected]
•Website:http://www.GEmultilin.com

1–2 P485 MODBUS TO PROFIBUS CONVERTER – USER GUIDE
INTRODUCTION
Document conventions
DESCRIPTION The following conventions are used throughout this document:
• Numbered lists provide sequential steps.
• Bulleted lists provide information, not procedural steps.
• The term ‘user’ refers to the person or persons responsible for installing the P485
Modbus to Profibus Converter in a network.
• Hexadecimal values are written in the format 0xNNNN, where NNNN is the
hexadecimal value.
• Decimal values are represented as NNNN, where NNNN is the decimal value.
• As in all communication systems, the terms “input” and “output” can be ambiguous,
since their meaning depends on which end of the link is being referenced. The
convention in this document is that “input” and “output” are always being referenced
to the master/scanner end of the link (see illustration below).
• The term “sub-network” is interchangeably used for “Modbus network”.
Figure 1-1: Input and output definition
GLOSSARY The following terminology is used in the P485 manual:
• Broadcaster: A protocol specific node in the sub-network scan that holds transactions
destined for all nodes.
• Command: A protocol specific transaction.
• Fieldbus: The network to which the converter is connected (Profibus for P485).
• Frame: A higher level series of bytes forming a complete telegram on the sub-network
(Modbus).
• Monitor: A tool for debugging the P485 and network connections.
• Node: A device in the scan list that defines the communication with a slave (GE relay)
on the Modbus sub-network.
• Scan list: List of configured slaves with transactions on the sub-network.
• Sub-network: Modbus network that logically is located on a subsidiary level with
respect to the fieldbus and to which the P485 acts as a gateway.
• Transaction: A generic building block that is used in the sub-network scan list and
defines the data that is sent out the sub-network.
Profibus
master
Slave GE Multilin
P485 Converter Slave
Modbus
network
Profibus network
OUT
IN
OUT
IN

INTRODUCTION
P485 MODBUS TO PROFIBUS CONVERTER – USER GUIDE 1–3
About the P485 Modbus to Profibus Converter
APPLICATION The P485 Modbus to Profibus Converter (or P485) acts as a gateway between the Modbus
protocol and a Profibus-DP network. Integration of industrial devices is enabled without
loss of functionality, control, and reliability, both when retrofitting to existing equipment as
well as when setting up new installations.
Figure 1-2: Typical applications
Features
GENERAL FEATURES • DIN-rail mountable
• Save/load configuration in flash
•CE,UL,andcULmarked
MODBUS NETWORK • RS232/RS422/RS485 communications
• Multi-drop or single-node configurations
• Modbus RTU Master mode
• Supports up to 50 commands
• Configuration via EnerVista P485/D485 Setup software
FIELDBUS INTERFACE
FEATURES
• Complete Profibus-DP slave functionality according to IEC 61158
• Node Address range: 1 to 99 using on board switches
• Baud rate range: 9.6 kbps to 12 Mbps. Auto baud rate detection supported.
• Transmission media: Profibus bus line, type A or B specified in IEC 61158
Profibus
master (PLC)
HMI
Profibus
slave
Profibus network
P485
PC for configuration
and monitoring
Multi-drop
Multi-node Modbus network
Single-node Modbus network
RS232 port
PC for configuration
and monitoring
Profibus slave
HMI
Profibus
master (PLC)
Profibus network
P485

1–4 P485 MODBUS TO PROFIBUS CONVERTER – USER GUIDE
INTRODUCTION
Ordering
ORDER CODES The following table illustrates the order codes for the P485 Modbus to Profibus Converter.
Specifications
MECHANICAL HOUSING
Plastic housing with snap-on connection to DIN-rail, protection class IP20
DIMENSIONS
L x W x H: 120 mm ×75 mm ×27 mm
(4.72-in ×2.95-in ×1.06-in)
PROTECTION CLASS
Protection class: IP20
ELECTRICAL
CHARACTERISTICS
POWER SUPPLY
Power: 24 V ±10% (for use in class 2 circuits)
POWER CONSUMPTION
Maximum power consumption: 280 mA on 24 V
Typically power consumption: approximately 100 mA
COMMUNICATIONS BAUD RATES
Baud rate (Profibus) 9.6, 19.2, 45.45, 93.75, 187.5, and 500 kbps; 1.5, 3, 6, and 12 Mbps
Baud rate (Modbus) 1200, 2400, 4800, 9600, 19200, 38400, and 57600 bps
I/O DATA
I/O input size: 244 bytes
I/O output size: 244 bytes
Total I/O size: 416 bytes
FEATURES AND INTERFACE
Communication profile: Profibus-DP
Supported features: synchronous, freeze, watchdog
Modbus interface: RS232, RS422, RS485
Profibus interface: RS485 (type A or B)
ENVIRONMENTAL RELATIVE HUMIDITY
The product is designed for a relative humidity of 0 to 95% non-condensing
TEMPERATURE
Operating: 0 to 55°C
Non Operating: –5 to 85°C
EMC COMPLIANCE CE-MARK
Certified according to European standards unless otherwise is stated
Emission: according to EN 50081-2:1993
Immunity: according to EN 61000-6-2:1999
UL/C-UL COMPLIANCE
This unit is an open type listed by the Underwriters Laboratories.
The certification has been documented by UL in file E214107.
Table 1–1: P485 order codes
P485 – *
Base unit P485 |P485 Modbus to Profibus Converter
CWith configuration cable
XNo configuration cable

P485 MODBUS TO PROFIBUS CONVERTER – USER GUIDE 2–1
GE Consumer & Industrial
P485 Modbus to Profibus
Converter
Chapter 2: Installation
Instal lation
Quick install
PROCEDURE 1. Snap the P485 on to the DIN-rail (see DIN-rail mounting on page 2–5).
2. Connect the Profibus cable (see Profibus connector on page 2–2).
3. Connect the serial Modbus network cable (see Modbus connector on page 2–4 for
details).
4. Connect a PC using the configuration cable (see Configuration cable on page 2–3).
5. Connect the power cable and apply power to the unit (see Power connector on page
2–4 for details).
6. Start the EnerVista P485/D485 Setup software.
7. Normally, the EnerVista P485/D485 Setup detects the correct serial port. If this does
not occur, select the correct port through the Port menu item.
8. Configure the P485 using EnerVista P485/D485 Setup and download the configuration
to the unit.
9. Configure and power-up the Modbus network device for communication.
Electrical installation
OVERVIEW The location of the various electrical connectors is shown below.

2–2 P485 MODBUS TO PROFIBUS CONVERTER – USER GUIDE
INSTALLATION
Figure 2-1: P485 electrical connections
PROFIBUS CONNECTOR The Profibus connector is indicated as Ain the figure above. This connector is used to
connect the P485 to the Profibus network.
The pin assignments for the Profibus connector are shown below.
Figure 2-2: Profibus connector
The following Profibus connectors are recommended:
• Profibus Max standard, part number 134928 and Profibus reversed, part number
104577, from http://www.erni.com
• Fast connect bus connector, part number 6GK1500-0FC00 or 6ES7 972-0BA50-0XA0,
from http://www.siemens.com
E
A
B
C
D
Table 2–1: Profibus connector pin assignments
Pin Signal Description
1- -
2- -
3 B-Line Positive RxD/TxD (RS485)
4 RTS * Request To Send
5 GNDBUS ** Isolated ground from the RS485 side
6 +5 V BUS ** Isolated +5V output from the RS485 side (80 mA maximum)
7- -
8 A-Line Negative RxD/TxD (RS485)
9- -
* Used in some equipment to determine the direction of transmission. However, in normal
applications only A-Line, B-Line and Shield are used.
** Used for bus termination. Some devices such as optical transceivers (RS485 to fibre optics) may
require power from these pins.
51
69
(female)

INSTALLATION
P485 MODBUS TO PROFIBUS CONVERTER – USER GUIDE 2–3
CONFIGURATION CABLE The PC connector is indicated as Bin Figure 2-1: P485 electrical connections on page 2–2.
This connector is used to connect the P485 to a PC using the configuration cable for
configuration and monitoring purposes.
A P485/D485 configuration cable can be purchased from GE Multilin. The wiring for the
configuration cable is shown below.
Figure 2-3: Configuration cable
The pinout for the modular 4/4 RJ11 connector (connects to the P485) is shown below.
Figure 2-4: Configuration cable (P485 end)
The pinout for the DSUB 9-pin serial plug (connects to the PC) is shown below.
Table 2–2: Configuration cable pin assignments (P485 end)
Pin Description
1 Signal ground
2 Signal ground
3 RS232 Rx, data input to P485
4 RS232 Tx, data output from P485
Table 2–3: Configuration cable pin assignments (PC end)
Pin Description
1 Not connected
2 RS232 Rx, data input to PC
3 RS232 Tx, data output from PC
4 Not connected
5 Ground
6 to 9 Not connected
1
2
3
4
5
6
7
8
9
1
2
3
4
D-sub 9 female (PC) Modular 4/4 RJ11 connector (P485)
Ground
Ground
Rx
Tx
RS232 Tx
RS232 Rx
Ground
Connects to PC serial port
Connects to P485
1
2
3
4

2–4 P485 MODBUS TO PROFIBUS CONVERTER – USER GUIDE
INSTALLATION
Figure 2-5: Configuration cable (PC end)
MODBUS CONNECTOR The Modbus connector is indicated as Cin Figure 2-1: P485 electrical connections on page
2–2. This connector is used to connect the P485 to the serial network. Based on the
configuration selected in the EnerVista P485/D485 Setup software, the corresponding
signals are activated.
Figure 2-6: Modbus connector
POWER CONNECTOR The power connector is indicated as Din Figure 2-1: P485 electrical connections on page
2–2. Use this connector to apply power to the P485.
Pin 1: +24 V DC;
Pin 2: ground
Use 60/75 or 75°C copper (CU) wire only. The terminal tightening torque must be between
5 to 7 lbs-in (0.5 to 0.8 nm).
Figure 2-7: Power connector
51
69
(female)
Table 2–4: Modbus connector pin assignments
Pin Description RS232 RS422 RS485
1 +5 V output (50 mA max)
2 RS232 Rx 3
3 RS232 Tx 3
4 Not connected
5 Ground 333
6 RS422 Rx + 3
7 RS422 Rx – 3
8 RS485 + / RS422 Tx+ 33
9 RS485 – / RS422 Tx– 33
51
69
(female)
NOTE
12

INSTALLATION
P485 MODBUS TO PROFIBUS CONVERTER – USER GUIDE 2–5
Mechanical installation
DIN-RAIL MOUNTING The DIN-rail connector is internally connected to the P485.
Figure 2-8: Mounting the P485 to the DIN-rail
To snap the P485 on, first press the P485 downwards (1) to compress the spring on the DIN-
rail connector, then push the P485 against the DIN-rail as to make it snap on (2)
To snap the P485 off, push the P485 downwards (1) and pull it out from the DIN-rail (2), as to
make it snap off from the DIN-rail.
Indicators and switches
STATUS INDICATORS The status indicators for the P485 Modbus to Profibus Converter are indicated below.
Figure 2-9: P485 status indicators
11
22
ON OFF
1
3
5
2
4
6

2–6 P485 MODBUS TO PROFIBUS CONVERTER – USER GUIDE
INSTALLATION
CONFIGURATION
SWITCHES
The configuration switches are used to set the Profibus node address. Normally, these
switches are covered by a plastic hatch. Note that the node address can not be changed
during runtime, i.e. the P485 requires a reset for any changes to have effect. Recycle the
power supply to reset the module
Figure 2-10: P485 configuration switches
The node address is configured using two rotary switches as follows:
Profibus node address = (Switch B×10) + (Switch A ×1)
Table 2–5: P485 status indicators
Number Description State Status
1 Profibus online Off Not online
Green Online
2 Profibus offline Off Not offline
Red Offline
3Notused- -
4Profibus
diagnostics
Off No diagnostics present
Red, flashing 1 Hz Error in configuration
Red, flashing 2 Hz Error in user parameter data
Red, flashing 4 Hz Error in initialisation
5 Subnet status *
(Modbus)
Off Power off
Green, flashing Initializing and not running
Green Running
Red Stopped or subnet error, or timeout
6 Device status Off Power off
Alternating Red/
Green
Invalid or missing configuration
Green Initializing
Green, flashing Running
Red, flashing If the device status LED is flashing in a
sequence starting with one or more red
flashes, note the sequence pattern and
contact GE Multilin
* This LED turns green when all transactions have been active at least once. This includes any
transactions using “change of state” or “change of state on trigger”. If a timeout occurs on a
transaction, this LED will turn red.
A
B

INSTALLATION
P485 MODBUS TO PROFIBUS CONVERTER – USER GUIDE 2–7
For example, to set the node address to 42, set switch A to “2” and switch B to “4”.
When removing the hatch, avoid touching the circuit boards and components. Exercise
caution when using tools to open the hatch.
Profibus installation procedure
PROFIBUS
CONFIGURATION TOOL
Each device on a Profibus-DP network is associated with a GSD file, which contains all
necessary information about the device. This file is used by the Profibus configuration tool
during configuration of the network. The file is available for download at the GE Multilin
website at http://www.GEmultilin.com (the GSD file is named ‘P48509E5.GSD’).
It is necessary to import the GSD file in the Profibus configuration tool in order to
incorporate the P485 as a slave in the network. The properties for the P485 must then be
configured from the Profibus configuration tool. This includes setting up the node address,
input/output data areas and offset address.
•Node address: The node address in the Profibus configuration tool should be set to
match the one selected using the on board configuration switches of the P485 (see
Configuration switches on page 2–6).
•Setting up input/output data areas: Input/output data are arranged as logic modules
in the Profibus configuration tool. Which modules to use depends on the application.
The modules are composed together in the “module list” for the P485 device.
It is possible to select modules freely to compose the required input/output sizes, see
example below.
•Offset address: The offset addresses can be chosen freely. However, certain
restrictions may apply depending on what PLC/Profibus master is used.
PROFIBUS NETWORK
TERMINATION
If the P485 is the last node on a Profibus segment, it is necessary to use a Profibus
connector with integrated termination switch.
• The termination switch should be set to ‘ON’ if...
– The P485 is the last physical node on a network segment
– No other termination is used at this end of the network
• The termination switch should be set to ‘OFF’ if...
– There are other nodes on either side of the P485 in the network segment
LINKS Additional information about the Profibus fieldbus system can be found at http://
www.profibus.com.
NOTE
Input/output bytes required Modules
4 inputs and 2 outputs 4 inputs + 2 outputs
7 inputs and 12 outputs 4 inputs + 2 inputs + 1 input + 8 outputs + 4 outputs
68 inputs 64 inputs + 4 inputs

2–8 P485 MODBUS TO PROFIBUS CONVERTER – USER GUIDE
INSTALLATION
Troubleshooting
DESCRIPTION Problem during configuration upload/download. The Config Line LED turns red.
• Serial communication failed – try again.
The serial port seems to be available, but it is not possible to connect to the P485.
• The serial port may be in use by another application. Exit EnerVista P485/D485 Setup
and close all other applications including the ones in the system tray and try again.
• Select another serial port and try again.
Poor performance.
• Right click ‘Modbus Network’ in the Navigation window and select ‘Modbus Network
Status’ to see status/diagnostic information about the Modbus network. If the P485
reports very many re-transmissions, check your cabling and / or try a lower baud rate
setting for the sub network (if possible).
• Is the Modbus Network Monitor in EnerVista P485/D485 Setup active? The Modbus
network monitor has a negative influence on the overall performance of the P485, and
should only be used when necessary.
• Is the Node Monitor in EnerVista P485/D485 Setup active? The node monitor has a
negative influence on the overall performance of the P485, and should only be used
when necessary.

P485 MODBUS TO PROFIBUS CONVERTER – USER GUIDE 3–1
GE Consumer & Industrial
P485 Modbus to Profibus
Converter
Chapter 3: Data exchange
Data ex change
Overview
DESCRIPTION Data from the fieldbus (Profibus) and the sub network (Modbus) is stored in an internal
memory buffer. This is a easy method for data exchange where the fieldbus control
system simply reads and writes data to pre-defined memory locations, and the serial sub
network also use the same internal memory buffer to read and write data. Refer to Figure
3-2: Data exchange overview on page 3–2 for details.
INTERNAL MEMORY
BUFFER STRUCTURE
The internal memory buffer can be seen as a memory space with three different types of
data; input data, output data and general data.
•Input data: This is data that should be sent to the fieldbus. The P485 can handle up to
244 bytes of input data. The total input/output data must not exceed 416 bytes.
•Output data: this is data recieved from the fieldbus. The P485 can handle up to 244
bytes of output data.
•General data: This data cannot be accessed from the fieldbus, and is used for
transfers between nodes on the sub-network, or as a general “scratch pad” for data.
The P485 can handle up to 1024 bytes of general data.
Figure 3-1: Internal memory buffer
Internal Memory Buffer
Output data
(up to 244 bytes)
Input data
(up to 244 bytes)
Sub Network
Fieldbus
General data
1024 bytes

3–2 P485 MODBUS TO PROFIBUS CONVERTER – USER GUIDE
DATA EXCHANGE
Figure 3-2: Data exchange overview
Memory Map
MEMORY LOCATIONS When configuring the sub-network, use the memory locations shown below:
The PLC exchanges data
via the Profibus network
between its internal input
area and the input area
of the P485 Profibus network
The PLC exchanges data
via the Profibus network
between its internal output
area and the output area
of the P485
The data in the input area of
the P485 contains data received
from nodes on the Modbus
sub-network (sent in to the P485
from the sub-network)
The data in the output area of
the P485 contains data received
from Profibus. In this case, it is
the CT PRIMARY setting of the
PQMII meter.
0x0000 0x0200 0x0400
Input data area Output data area General data area
Modbus sub-network
Current Ia CT PRIMARY
Internal memory buffer
of the P485
PLC memory
I/O inputs I/O outputs
Current Ia CT PRIMARY
Modbus slave (e.g. PQMII)
CT PRIMARY setting
Current Ia actual value
Address Contents Access
0x0000 to 0x0001 Status register read/write
0x0002 to 0x00F3 Input data area read/write
0x00F4 to 0x01FF Reserved -
0x0200 to 0x0201 Control register read only
0x0202 to 0x02F3 Output data area read only
0x02F4 to 0x03FF Reserved -
0x0400 to 0x7FF General data area read/write