ProSoft Technology MVI56E-MCM/MCMXT User Manual
Page 130

Reference
MVI56E-MCM ♦ ControlLogix Platform
User Manual
Modbus Communication Module
Page 130 of 199
ProSoft Technology, Inc.
June 18, 2014
Formatted Pass-Through Blocks (9956 to 9959)
If one or more of the Slave Ports on the module are configured for the Formatted
Pass-through mode, the module will pass blocks with identification codes of 9956
to 9959 to the processor for each received write command. Any Modbus function
5, 6, 15 or 16 commands will be passed from the port to the processor using
these block identification numbers. Ladder logic must handle the receipt of all
Modbus write functions to the processor and must respond as expected to
commands issued by the remote Modbus Master device. The structure of these
formatted Pass-through blocks is shown in the following tables:
Function 5
Pass-Through Block 9958 from Module to Processor
Word Offset
Description
Length
0
0
1
1
9958
1
2
1
1
3
Bit Address
1
4 to 248
Modbus data received
245
249
9958
1
The ladder logic will be responsible for parsing and copying the received
message and performing the proper control operation as expected by the Master
device. The processor must then respond to the Pass-through block with a write
block with the following format.
Response Block 9958 from Processor to Module
Word Offset
Description
Length
0
9958
1
1 to 247
Spare
247
This will inform the module that the command has been processed and can be
cleared from the pass-through queue.
Function 6 and 16
Pass-Through Blocks 9956 or 9957 from Module to Processor
Offset
Description
Length
0
0
1
1
9956/9957 (Floating-point)
1
2
Number of data words
1
3
Data Address
1
4 to 248
Data
245
249
9956/9957
1