ProSoft Technology MVI69L-MBS - Manual (Page 135)

MVI69L-MBS ♦ CompactLogix Platform Reference
Communication Module User Manual
ProSoft Technology, Inc. Page 135 of 154
January 6, 2014
7.4.13 Pass-through Formatted Block for Functions 6 and 16 with
Word Data Block
Block 9956: Pass-through Formatted Block for Functions 6 and 16 with Word
Data Block
If the slave port on the module are configured for formatted pass-through mode,
the module sends input image blocks with identification codes of 9956, 9957,
9958 or 9959 to the processor for each write command received. Any incoming
Modbus Function 5, 6, 15 or 16 command is passed from the port to the
processor using a block identification number that identifies the Function Code
received in the incoming command.
The MBS Add-On Instruction handles the receipt of all Modbus write functions
and to respond as expected to commands issued by the remote Modbus Master
device.
Block 9956: Request from Module to Processor
Offset Description
0 Read Block ID: 9956
1 Write Block ID: 9956
2 Number of word registers in Modbus data set
3 Starting address for Modbus data set
4 to 239 Data
The ladder logic is 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 control block with an
output image write block with the following format.
This informs the module that the command has been processed and can be
cleared from the pass-through queue.
Block 9956: Response from Processor to Module
Offset Description
0 Write Block ID: 9956
1 to 239 Spare