ProSoft Technology MVI56E-MNETC - Manual (Page 52)

Guide to the MVI56E-MNETC User Manual MVI56E-MNETC ♦ ControlLogix Platform
User Manual Modbus TCP/IP Client Enhanced Communication Module
Page 52 of 183 ProSoft Technology, Inc.
February 3, 2013
Command List Overview
In order to interface the module with Modbus TCP/IP server devices, you must
construct a command list. The commands in the list specify the server device to
be addressed, the function to be performed (read or write), the data area in the
device to interface with, and the registers in the internal database to be
associated with the device data. The Client command list supports up to 16
commands.
The command list is processed from top (command #1) to bottom. A poll interval
parameter is associated with each command to specify a minimum delay time in
tenths of a second between the issuances of a command. If the user specifies a
value of 10 for the parameter, the command will be executed no more frequently
than every 1 second.
NOTE: If you are using only Event Commands or issuing commands from the
Command List using Command Control from ladder logic, it is likely that the
module will not leave any inactive TCP/IP socket connections open for more than
60-seconds. To maintain an open socket connection, your configuration or
application must be designed so that at least one command is issued to each
server connection at less than 60-second intervals. The 60-second connection
timeout is not user-configurable and was put in place to prevent long delays
between commands.
Commands Supported by the Module
The format of each command in the list depends on the Modbus Function Code
being executed.
The following table lists the functions supported by the module.
Function Code Definition Supported in Client Supported in Server
1 Read Coil Status X X
2 Read Input Status X X
3 Read Holding Registers X X
4 Read Input Registers X X
5 Force (Write) Single Coil X X
6 Preset (Write) Single Register X X
7 Read Exception Status X X
8 Diagnostics X
15 Force (Write) Multiple Coils X X
16 Preset (Write) Multiple
Registers X X
22 Mask Write 4X X
23 Read/Write X
Each command list record has the same general format. The first part of the
record contains the information relating to the communication module and the
second part contains information required to interface to the Modbus TCP/IP
server device.