ProSoft Technology MVI56E-MCMR - Manual (Page 169)

MVI56E-MCMR ♦ ControlLogix Platform Reference
Modbus Communication Module with Reduced Data Block User Manual
ProSoft Technology, Inc. Page 169 of 225
May 13, 2014
Master Command List
In order to function in the Master Mode, you must define the module’s Master
Command List. This list contains up to 100 individual entries, with each entry
containing the information required to construct a valid command. A valid
command includes the following items:
 Command enable mode: (0) disabled, (1) continuous or (2) conditional
 Slave Node Address
 Command Type: Read or Write up to 125 words (16000 bits) per command
 Database Source and Destination Register Address: The addresses where
data will be written or read.
 Count: The number of words to be transferred - 1 to 125 on FC 3, 4, or 16.
Select the number of bits on FC 1, 2, 15.
As the list is read in from the processor and as the commands are processed, an
error value is maintained in the module for each command. This error list can be
transferred to the processor. The following tables describe the error codes
generated by the module.
Note: 125 words is the maximum count allowed by the MODBUS protocol. Some field devices may
support less than the full 125 words. Check with your device manufacturer for the maximum count
supported by your particular slave.