ProSoft Technology MVI56E-MCM/MCMXT - Manual (Page 52)

Configuration as a Modbus Master MVI56E-MCM ♦ ControlLogix Platform
User Manual Modbus Communication Module
Page 52 of 199 ProSoft Technology, Inc.
June 18, 2014
The following illustration shows the command required to write these 7 Floating-
Point values.
Based on the IntAddress and the configuration within the
MCM.CONFIG.M
OD D EF section for WriteStartReg and WriteRegCount, the data
from the tag MCM.DATA.W RITE D ATA [0] TO [6] will be written to Modbus
addresses 47001 to 47007 of the Slave device node #1.
Note: A swap code may be required to put the data in the proper format for the Slave device.
2.5 Command Control and Event Command
You can use Command Control and Event Commands in Modbus Master mode
to change the command execution based on some conditions in ladder. The
module goes through the command list sequentially. For example:
 The module executes MCM.CONFIG.P
ORT 1M ASTER C MD [0]
 After completing that command, it will then execute
MCM.CONFIG.P ORT 1M ASTER C MD [1], then
MCM.CONFIG.P ORT 1M ASTER C MD [2], and so on.
You can use Command Control and Event Command to issue a command at the
top of the command queue, interrupting the regular command list execution.
You would typically use Command Control and Event Command to
 issue a reset to a device on a once a day basis
 poll for end of hour data
 issue special commands on the startup of a process or the changing of a
batch
Important: Because these special command blocks will interrupt the normal polling list, you should
use them sparingly, to avoid interrupting your normal data transfer. Make sure that the data to be
written to the device contains the latest value from the WriteData tag that corresponds to the
Command Control or Event Command.