Magnetrol Jupiter JM4 User manual

HART®to Modbus®Adaptor
Operating Manual
Firmware Version 1.7
2014/68/EU
Eclipse®Model 706
Guided Wave Radar Level Transmitter
Jupiter®Model JM4
Magnetostrictive Level Transmitter
Pulsar®Model R96
Pulse Burst Radar Level Transmitter

41-621.1 HART®to Modbus®Adaptor Operating Manual 3
TABLE OF CONTENTS
INTRODUCTION ............................................................................................................................5
QUICK START PROCEDURE..........................................................................................................8
SETUP PROCEDURES ....................................................................................................................9
1. CONFIGURING COMMUNICATIONS SETTINGS IN THE HMA...........................................................9
2. READING AND WRITING REGISTERS IN THE HMA .......................................................................12
3. USING A DTM WITH THE HMA...................................................................................................16
4. USING A HANDHELD FIELD COMMUNICATOR WITH THE HMA....................................................17
5. BASIC MODBUS RTU COMMUNICATION OVER RS-485................................................................18
6. BASIC MODBUS RTU COMMUNICATION OVER RS-232................................................................19
7. BASIC MODBUS ASCII COMMUNICATION OVER RS-485 ..............................................................20
8. MODBUS RTU COMMUNICATION IN HMA MODE.......................................................................22
9. MODBUS RTU COMMUNICATION IN DEVICE MODE ...................................................................26
10. MODBUS RTU COMMUNICATION IN SINGLE MODBUS DEVICE MODE.........................................29
11. BASIC LEVELMASTER COMMUNICATION....................................................................................31
12. ADDITIONAL LEVELMASTER COMMANDS...................................................................................37
13. AUTO SWITCHING BETWEEN MODBUS RTU/ASCII AND HART OVER RS-485 COMMUNICATION....42
14. AUTO SWITCHING BETWEEN LEVELMASTER AND HART OVER RS-485 COMMUNICATION ............46
15. HMA DIAGNOSTICS...................................................................................................................51
16. EMERSON ROC 800...................................................................................................................55
17. ABB TOTALFLOW XRC –MODBUS RTU / ASCII ............................................................................64
18. ABB TOTALFLOW XRC –LEVELMASTER ......................................................................................81
19. THERMOSCIENTIFIC AUTOPILOT PRO –MODBUS RTU / ASCII .....................................................93
APPENDICES ..............................................................................................................................103
A. HMA TERMINAL BLOCK LAYOUT..............................................................................................103
B. HMA DIP SWITCH SETTINGS ....................................................................................................104
C. HMA LED INDICATORS ............................................................................................................104
D. HMA SYSTEM CONNECTION DIAGRAM ....................................................................................105
E. NOMENCLATURE TABLE..........................................................................................................105
F. MODBUS RTU COMMUNICATION REGISTERS...........................................................................106
G. MODBUS ASCII COMMUNICATION REGISTERS .........................................................................107
H. LEVELMASTER COMMUNICATION REGISTERS ..........................................................................108
I. HART OVER RS485 COMMUNICATION REGISTERS ....................................................................109
J. HMA DIAGNOSTICS MODBUS REGISTERS.................................................................................110
K. HMA DEVICE INFORMATION MODBUS REGISTERS....................................................................111
L. MODEL 706, MODEL JM4 MODBUS REGISTERS ........................................................................112

4 41-621.1 HART®to Modbus®Adaptor Operating Manual
M. MODEL 705 3X MODBUS REGISTERS........................................................................................113
N. MODEL R82 R2 MODBUS REGISTERS........................................................................................114
O. MODEL RX5 MODBUS REGISTERS ............................................................................................115
P. MODEL 355 MODBUS REGISTERS ............................................................................................116
Q. ENHANCED JUPITER MODBUS REGISTERS ................................................................................117
R. E3 MODULEVEL MODBUS REGISTERS ......................................................................................118
S. MODEL R96 MODBUS REGISTERS ............................................................................................119
T. LEVELMASTER ERROR AND WARNING CODES ..........................................................................120
U. LEVEL UNIT CODES..................................................................................................................122
V. PARAMETER CODES................................................................................................................122

41-621.1 HART®to Modbus®Adaptor Operating Manual 5
INTRODUCTION
This document is intended to provide a guide for utilizing the various features of the Magnetrol HART
to Modbus Adaptor (HMA). For each feature, a step-by-step procedure is provided to demonstrate
how to set up the HMA and attached HART devices for a particular configuration. Other configurations
are possible with various combinations of the number of HART to Modbus Adapters on a single RS-485
line and the number and type of Magnetrol HART devices attached to those HMAs. The operations in
those configurations can be accomplished by extending the procedures provided in this document.
Additionally, it is not required to use the Modbus RTUs or host applications shown in this document.
Any RTU or host application that allows for reading and writing Modbus registers to a slave device can
be used.
The HART to Modbus Adaptor (HMA) is designed to allow Magnetrol HART transmitters to be utilized
in a Modbus®
1
system. The following Modbus protocols are supported:
•Modbus RTU –Function codes 3, 4, 6, and 16
•Modbus ASCII –Function codes 3, 4, 6, and 16
•Levelmaster –Commands Uxx?, UxxF?, UxxOL?, and UxxOLxxxx?
A unique feature of the HMA is that it will support up to five attached HART devices; one in the same
housing as the HMA, and up to four external devices attached through a 4-20 mA loop.
•The attached devices do not have to all the same type transmitter.
•The HMA provides power for all attached HART units.
•The attached units should be set to a fixed 4 mA loop current.
Communication
Within the above protocols, it is possible to configure communications parameters such as baud rate,
parity, stop bits, etc. to match the settings for a particular Modbus Remote Terminal Unit (RTU) or
host.
To ensure a standard method to communicate with the HMA, setting DIP switch positions 1 –3 to OFF,
and 4 to ON, (see Appendix A) will configure the HMA to communicate via Modbus RTU with the
default communications settings shown in Appendix F.
1
Modbus®is a registered trademark of Schneider Electric, licensed to the Modbus Organization, Inc.

6 41-621.1 HART®to Modbus®Adaptor Operating Manual
Operating Modes
Modbus RTU and Modbus ASCII
When using the Modbus RTU and ASCII protocols, the HMA can be used in several ways:
1. HMA with a single transmitter (HMA mode) –The Modbus host addresses the HMA directly,
using the address of the HMA. The registers in the HMA for the attached device follow the
numbers listed for Slave 1 in the device register appendices L through S. In this mode, the
allowable Modbus addresses are in the range of 1 through 247. This is the default
configuration for the HMA.
2. HMA with multiple transmitters and one Modbus address (HMA mode) –The Modbus host
addresses the HMA directly, using only the address of the HMA. The registers in the HMA for
each attached device depend on the slave number of the attached devices as listed in
Appendices L through S. The HMA will appear to be a Modbus device capable of providing
multiple level measurements. In this mode, the allowable Modbus addresses are in the range
of 1 through 247.
3. HMA with multiple transmitters and multiple Modbus addresses (Device mode) –The Modbus
host addresses the HART devices directly, using the HART Poll Address of each device as the
Modbus address. (The HMA is essentially transparent.) The HART devices will appear to be
native Modbus devices to the Modbus host. The registers for each attached device type are the
same regardless of the poll address. The registers in the HMA for each attached device follow
the numbers listed for Slave 1 in the device register appendices L through S. In this mode, the
allowable Modbus/HART addresses are limited to the range of 1 through 62.
4. Single Modbus Device –The HMA is connected to only the HART device present in the same
transmitter housing. The HART poll address of the HART device and the Modbus poll address of
the HMA are the same. Changing the HART poll address of the attached transmitter will
automatically change the Modbus poll address of the HMA to match. Essentially, they appear
to a Modbus master as a single native Modbus device. The registers in the HMA for the
attached device follow the numbers listed for Slave 1 in the device register appendices L
through S. In this mode, the allowable Modbus/HART addresses are limited to the range of 1
through 62.
LevelMaster
When using the LevelMaster protocol, the HMA will appear to be invisible to the LevelMaster host.
This is due to the limited command set available with LevelMaster. Instead, the attached HART devices
will appear to be native LevelMaster devices. They will respond to the Modbus poll address equivalent
to their HART poll address. In this mode, the allowable Modbus/HART addresses are limited to the
range of 1 through 62.

41-621.1 HART®to Modbus®Adaptor Operating Manual 7
Supported Device Parameters
Not all of the parameters for a particular Magnetrol HART transmitter are supported by the HMA using
Modbus communication. For each device type, the parameters that are available have been chosen to
represent the most commonly for optimization and troubleshooting. The available parameters are
listed in Appendices L through S.
Full Device Configuration
Using a HART DD or DTM, the full range of HART transmitter parameters can be accessed to configure
an attached HART device. There are three ways to connect a HART host to the transmitter enclosed
with the HMA. In each case, the HART Poll Address of the attached device must be used for
communication rather than the Modbus poll address of the connected HMA.
1. A HART modem can be connected directly to the HART terminal block on the HMA. The HMA
will always act as a primary master on the HART loop. Therefore, if connecting another HART
host to the terminal HART block, that additional host must either be capable of automatically
setting itself to be a secondary master, or be manually configured as a secondary master. Note
that the HART terminal block has a built-in 250-ohm resistor to facilitate HART communication.
See the section on using a DTM with the HMA.
2. The HMA is capable of passing HART commands using the RS-485 connection to the attached
devices.
3. A TTL-232R-3V3-AJ USB to TTL cable or equivalent can be connected between the computer
running the DD host or DTM frame (such as PACTware) and the audio jack on the electronics
module of the transmitter located underneath the LCD display. The HART host can be set as
either a primary or secondary master. This feature is available on the Model 706 Guided Wave
Radar, Model JM4 Magnetostrictive, and Model R96 Radar devices.

8 41-621.1 HART®to Modbus®Adaptor Operating Manual
QUICK START PROCEDURE
The following procedure demonstrates basic steps for configuring a Magnetrol transmitter containing a
HART to Modbus Adaptor (HMA) for use with a Modbus system. The example given is for an
installation where a single HART transmitter is attached to the HMA.
More complete instructions are provided in the SETUP PROCEDURES section as well as other
configurations and communication protocols.
1. Connect an RS-485 communications cable to the RS-485 terminal block of the HMA:
1.1. Receive/Transmit Data lead (+, A) connected to the positive terminal
1.2. Receive/Transmit Data lead (–, B) connected to the negative terminal.
1.3. Connect a 120resistor between the two RS-485 terminal block positions.
1.4. Connect the other end of the cable to a PC which has a Modbus host application installed.
2. Ensure that the DIP switches on the HMA are set as follows:
2.1. 1 == OFF (Default Config Mode)
2.2. 2 == OFF
2.3. 3 == OFF
2.4. 4 == ON.
See Appendix A for the location of the DIP switch, and Appendix B for a legend of the four switch
positions.
3. Connect the device containing the HMA to a power supply via the power terminal block.
4. Apply power to the HMA.
5. Set the Modbus host application to communicate via the default Modbus RTU communication
settings shown in Appendix F.
6. Set registers 3000 through 3006 to the desired communication settings for use with the host
system. Register 3001 (Slave address) should be set to the Modbus address desired for
communicating with the HMA.
7. Ensure that register 3007 (HMA Mode) is set to 0.
8. Change register 3012 to a value of 0. This will cause the HMA to scan the attached HART device at
initial start-up, and record the poll address and other information for the device.
9. If RS-232 communication is to be used, set DIP switch 3 to ON, and DIP switch 4 to OFF.
10. Change DIP switch 1 to ON. The HMA will automatically reboot, scan for the attached device, and
configure itself for the communication protocol and Modbus address selected in step 6.
11. By viewing the appropriate registers, verify that the desired transmitter measured values are being
actively read by the Modbus host.
12. The device is ready to use.

41-621.1 HART®to Modbus®Adaptor Operating Manual 9
SETUP PROCEDURES
1. Configuring communications settings in the HMA
1.1. Purpose
This procedure instructs how to configure HART to Modbus Adaptor (HMA) communications using a
basic Modbus master simulator application. The procedure can also be performed using any Modbus
master that permits reading and writing of the appropriate registers in the HMA.
To ensure that there is a known communication configuration for the HMA, position 1 of the DIP
switch is used to select between a fixed communication setting and a user-configurable setting. When
the switch is set to OFF, the HMA communicates using Modbus RTU with a poll address of 247 at 9600
baud, 8 data bits, no parity, and 1 stop bit. When in the default configuration, the user-selectable
communication settings can be adjusted. When the user communication settings are desired to be
used, position 1 of the DIP switch should be set to ON, and then input power cycled. Changing back to
the fixed default settings also requires a power cycle.
1.2. Equipment
Item
Manufacturer
Model
HART to Modbus Adaptor
MII
031-2859-001
USB Communications cable
FDTIchip
USB-RS485-WE
Termination resistor
-
120
Modbus host application
www.modbustools.com
Modbus Poll
Power Supply
-
20-24V, 0.5A
1.3. Setup
Connect the HMA to a power supply via the power terminal block. Connect an RS-485 communications
cable to the RS-485 terminal block of the HMA, with the Receive/Transmit Data+ A lead (orange) on
the positive terminal and the Receive/Transmit Data–B lead (yellow) on the negative terminal.
Connect a 120resistor between the two RS-485 terminal block positions. Connect the other end of
the cable to a PC which has a Modbus host application.
1.4. Procedure
1.4.1 Ensure that the DIP switches on the HMA are set to 1 == OFF (Default Config Mode), 2 ==
OFF, 3 == OFF, 4 == ON. See Appendix A for the location of the DIP switch, and Appendix
B for a legend of the four switch positions.
1.4.2 Open the Modbus Poll application.

10 41-621.1 HART®to Modbus®Adaptor Operating Manual
1.4.3 Select Connection\Connect from the menu bar, ensure that the connection settings are as
follows, and then click OK. Note that the USB Serial Port setting needs to match the port
number for the communication cable that is being used.
1.4.4 Open or click on an Mbpoll window, select Setup\Read\Write Definition from the menu
bar, ensure that the settings are as follows, and then click OK:

41-621.1 HART®to Modbus®Adaptor Operating Manual 11
1.4.5 Verify that the values in the registers listed in the Mbpoll window match the values for the
desired Modbus protocol settings. Refer to Appendix F for the HMA Communication
settings. If the settings do not match, double-click on a value that needs to be changed in
order to open the Write Single Register dialog, enter the new value, and then click on
Send.
1.4.6 Change DIP switch 1 to ON. This sets the device to run in the selected communications
mode.
1.4.7 If communication at the new settings is not achieved, change DIP switch 1 to OFF. This
sets the device to run in the default Modbus RTU communications mode. Check the
communication setting registers to ensure that the desired values are present.

12 41-621.1 HART®to Modbus®Adaptor Operating Manual
2. Reading and writing registers in the HMA
2.1. Purpose
This procedure instructs how to read and write HART to Modbus Adaptor (HMA) registers using a basic
Modbus master simulator application. The procedure can also be performed using any Modbus master
that permits reading and writing of the appropriate registers in the HMA.
2.2. Equipment
Item
Manufacturer
Model
HART to Modbus Adaptor
MII
031-2859-001
USB Communications cable
FDTIchip
USB-RS485-WE
Termination resistor
-
120
Modbus host application
www.modbustools.com
Modbus Poll
Power Supply
-
20-24V, 0.5A
2.3. Setup
Connect the HMA to a power supply via the power terminal block. Connect an RS-485 communications
cable to the RS-485 terminal block of the HMA, with the Receive/Transmit Data+ A lead (orange) on
the positive terminal and the Receive/Transmit Data–B lead (yellow) on the negative terminal.
Connect a 120resistor between the two RS-485 terminal block positions. Connect the other end of
the cable to a PC which has a Modbus host application.
2.4. Procedure
2.4.1 Ensure that the DIP switches on the HMA are set to 1 == OFF (Default Config Mode), 2 ==
OFF, 3 == OFF, 4 == ON. See Appendix A for the location of the DIP switch, and Appendix
B for a legend of the four switch positions.
2.4.2 Open the Modbus Poll application.

41-621.1 HART®to Modbus®Adaptor Operating Manual 13
2.4.3 Select Connection\Connect from the menu bar, ensure that the connection settings are as
follows, and then click OK. Note that the USB Serial Port setting needs to match the port
number for the communication cable that is being used.
.

14 41-621.1 HART®to Modbus®Adaptor Operating Manual
2.4.4 To read an input register, open or click on an Mbpoll window, and select
Setup\Read\Write Definition from the menu bar. Set the Slave ID to match the Modbus
Poll Address of the HMA. Set the Function to ’04 Read Input Registers (3x)’. Using
Appendices L through S, set the Address, Quantity and Display type in the pop-up dialog
as required. Then click OK. The register value should appear in the Mbpoll window.
In general, the Address should be set to the number of the first register to be accessed.
(Address numbers are listed in the Modbus Register Number columns in the appendices.)
The Quantity should be set to the sum of the individual sizes of sequential registers to be
accessed. In the below example, four registers are to be read and since each have a size
of 2 (listed in the Number column in the appendices).

41-621.1 HART®to Modbus®Adaptor Operating Manual 15
2.4.5 To read a holding register, open or click on an Mbpoll window, and select
Setup\Read\Write Definition from the menu bar. Set the Slave ID to match the Modbus
Poll Address of the HMA. Set the Function to ’03 Read Holding Registers (4x)’. Using
Appendices L through S, set the Address, Quantity and Display type in the pop-up dialog
as required. Then click OK. The register value should appear in the Mbpoll window.
2.4.6 To write a holding register, double-click on the register value displayed in step 2.4.6.
Enter the new value and click on ‘Send. Confirm that the new value appears in the Mbpoll
window.

16 41-621.1 HART®to Modbus®Adaptor Operating Manual
3. Using a DTM with the HMA
3.1. Purpose
This procedure instructs how to connect a HART DTM to the HMA to configure or troubleshoot an
attached HART transmitter.
3.2. Equipment
Item
Manufacturer
Model
HART to Modbus Adaptor
MII
031-2859-001
Power Supply
-
20-24V, 0.5A
PACTware
PACTware Consortium
Version 4.1 or higher
HART Modem
MacTek
Viator
Level transmitter
MII
Model 706
Probe
MII
Model 706 compatible
3.3. Setup
Connect the HMA, with an attached HART transmitter, to a power supply via the power terminal block.
Connect the HART Modem to the HART terminal block on the HMA. Note that the HMA provides 24
VDC on the terminal block and contains an internal 250-ohm resistor, so the modem can be directly
connected to the terminal block.
3.4. Procedure
3.4.1 Start PACTware.
3.4.2 Add a HART Comm DTM to the Project.
3.4.3 Left click on the Comm DTM in the Project tree and add a DTM to the Project for the listed
device.
3.4.4 Right-click on the Comm DTM item and select Parameter. Select the correct COM port for
the HART modem, set the Start address and End address to match the HART Poll Address
for the attached device. (The Poll Address can be read from the Device Setup\Advanced
Config\Analog Output menu on the transmitter’s local display.) Set the Comm DTM to be
a secondary master, then click OK.
3.4.5 Right-click on the Comm DTM item and select Additional functions\Change dtm address.
Click on the Change address button. Select the address number corresponding to the
attached Model 706 device, then click Close.
3.4.6 Right-click on the Comm DTM item and select Connect.
3.4.7 Double click on the transmitter entry in the Project tree to open the Online
parameterization window.
3.4.8 All features of the DTM will be available. Note that since the DTM is acting as a secondary
master and the HMA is periodically sending commands as the primary master, the
response of the DTM will be slower than when it is connected directly to a transmitter.

41-621.1 HART®to Modbus®Adaptor Operating Manual 17
4. Using a Handheld Field Communicator with the HMA
4.1. Purpose
This procedure instructs how to connect a handheld communicator, such as the Emerson 475, to the
HMA to configure or troubleshoot an attached HART transmitter.
4.2. Equipment
Item
Manufacturer
Model
HART to Modbus Adaptor
MII
031-2859-001
Power Supply
-
20-24V, 0.5A
PACTware
PACTware Consortium
Version 4.1 or higher
Field Communicator
Emerson
475
Level transmitter
MII
Model 706
Probe
MII
Model 706 compatible
4.3. Setup
Connect the HMA, with an attached HART transmitter, to a power supply via the power terminal block.
Connect the field communicator to the HART terminal block on the HMA. Note that the HMA provides
24 VDC on the terminal block and contains an internal 250-ohm resistor, so the field communicator can
be directly connected to the terminal block.
4.4. Procedure
4.4.1 Start the field communicator.
4.4.2 Ensure that the field communicator is configured to scan for the HART Poll Address of the
transmitter. (The Poll Address can be read from the Device Setup\Advanced
Config\Analog Output menu on the transmitter’s local display.)
4.4.3 When the field communicator finds the device, select it from the communicator’s menu.
4.4.4 All features of the HART DD for the transmitter will be available. Note that since the field
communicator is acting as a secondary master and the HMA is periodically sending
commands as the primary master, the response of the field communicator will be slower
than when it is connected directly to a transmitter.

18 41-621.1 HART®to Modbus®Adaptor Operating Manual
5. Basic Modbus RTU Communication over RS-485
5.1. Purpose
This procedure instructs how to configure the HART to Modbus Adaptor (HMA) to support the Modbus
RTU protocol over RS-485.
5.2. Equipment
Item
Manufacturer
Model
HART to Modbus Adaptor
MII
031-2859-001
RS485 Communications cable
FDTIchip
USB-RS485-WE
Termination resistor
-
120
Modbus host application
www.modbustools.com
Modbus Poll
Power Supply
-
20-24V, 0.5A
Level transmitter
MII
Model 706
Probe
MII
Model 706 compatible
5.3. Setup
Connect the HMA to a power supply via the power terminal block. Connect an RS-485 communications
cable to the RS-485 terminal block of the HMA, with the Receive/Transmit Data+ A lead (orange) on
the positive terminal and the Receive/Transmit Data–B lead (yellow) on the negative terminal.
Connect a 120resistor between the two RS-485 terminal block positions. Connect the other end of
the cable to a PC which has a Modbus host application.
5.4. Procedure
5.4.1 Using Procedure 1, ensure that registers 3000 through 3007 of the HMA match the values
for the Modbus RTU protocol settings used by the intended Modbus master. Refer to
Appendix F for the HMA Communication settings. If the settings do not match, double-
click on a value that needs to be changed in order to open the Write Single Register
dialog, enter the new value, and then click on Send.
5.4.2 Change DIP switch 1 to ON.
5.4.3 Connect the HMA to a Modbus master.
5.4.4 Apply power to the HMA.
5.4.5 Verify that the Modbus master is receiving responses from the HMA (Tx is increasing) and
that there are no communication errors being reported.

41-621.1 HART®to Modbus®Adaptor Operating Manual 19
6. Basic Modbus RTU Communication over RS-232
6.1. Purpose
This procedure instructs how to configure the HART to Modbus Adaptor (HMA) to support the Modbus
protocol over RS-232.
6.2. Equipment
Item
Manufacturer
Model
HART to Modbus Adaptor
MII
031-2859-001
RS485 Communications cable
FDTIchip
USB-RS485-WE
RS232 Communications cable
FDTIchip
USB-RS232-WE-1800-BT_0.0
Termination resistor
-
120
Modbus host application
www.modbustools.com
Modbus Poll
Power Supply
-
20-24V, 0.5A
Level transmitter
MII
Model 706
Probe
MII
Model 706 compatible
6.3. Setup
Connect the HMA to a power supply via the power terminal block. Connect an RS-485 communications
cable to the RS-485 terminal block of the HMA, with the Receive/Transmit Data+ A lead (orange) on
the positive terminal and the Receive/Transmit Data–B lead (yellow) on the negative terminal.
Connect a 120resistor between the two RS-485 terminal block positions. Connect the other end of
the cable to a PC which has a Modbus host application.
6.4. Procedure
6.4.1 Using Procedure 1, ensure that registers 3000 through 3007 of the HMA match the values
for the Modbus RTU protocol settings used by the intended Modbus master. Refer to
Appendix F for the HMA Communication settings. If the settings do not match, double-
click on a value that needs to be changed in order to open the Write Single Register
dialog, enter the new value, and then click on Send.
6.4.2 Change the DIP switches 3 and 4 to 3 == ON, 4 == OFF.
6.4.3 Change DIP switch 1 to ON. This sets the device to run in the selected communications
mode.
6.4.4 Disconnect the RS-485 communication cable from the HMA.
6.4.5 Connect the HMA to a Modbus master using a RS-232 communications cable. Connect
the master’s RS-232 TX line (orange) to the ‘+‘ position of the RS-485 terminal block, and
the RX line (yellow) to the ‘-‘ position.
6.4.6 Verify that the Modbus master is receiving responses from the HMA (Tx is increasing) and
that there are no communication errors being reported.

20 41-621.1 HART®to Modbus®Adaptor Operating Manual
7. Basic Modbus ASCII Communication over RS-485
7.1. Purpose
This procedure instructs how to configure the HART to Modbus Adaptor (HMA) to support the Modbus
ASCII protocol.
7.2. Equipment
Item
Manufacturer
Model
HART to Modbus Adaptor
MII
031-2859-001
RS485 Communications cable
FDTIchip
USB-RS485-WE
Termination resistor
-
120
Modbus host application
www.modbustools.com
Modbus Poll
Power Supply
-
20-24V, 0.5A
7.3. Setup
Connect the HMA to a power supply via the power terminal block. Connect an RS-485 communications
cable to the RS-485 terminal block of the HMA, with the Receive/Transmit Data+ A lead (orange) on
the positive terminal and the Receive/Transmit Data–B lead (yellow) on the negative terminal.
Connect a 120resistor between the two RS-485 terminal block positions. Connect the other end of
the cable to a PC which has a Modbus host application.
7.4. Procedure
7.4.1 Using Procedure 1, ensure that registers 3000 through 3007 of the HMA match the values
for the Modbus ASCII protocol settings used by the intended Modbus master. Refer to
Appendix G for the HMA Communication settings. If the settings do not match, double-
click on a value that needs to be changed in order to open the Write Single Register
dialog, enter the new value, and then click on Send.
7.4.2 Change DIP switch 1 to ON. This sets the device to run in the selected communications
mode.
7.4.3 Verify that the device is not communicating with the Modbus Poll application.
7.4.4 Select Connection\Disconnect from the Modbus Poll menu bar.