ProSoft Technology MVI56-MCM User Manual

Reference MVI56-MCM ♦ ControlLogix Platform
Modbus Communication Module
ProSoft Technology, Inc. Page 99 of 159
July 24, 2008
8.2.11 Pass-Through Control Blocks
Unformatted Pass-Through Control Blocks
If one or more of the slave ports on the module are configured for the
unformatted pass-through mode, the module will pass blocks with identification
codes of 9996 to the processor for each received write command. Any Modbus
function 5, 6, 15 and 16 commands will be passed from the port to the processor
using this block identification number. Ladder logic must handle the receipt of all
Modbus write functions to the processor and to respond as expected to
commands issued by the remote Modbus master device. The structure of the
unformatted pass-through control block is shown in the following table:
Offset Description Length
0 0 1
1 9996 1
2 Number of bytes in Modbus message 1
3 to 248 Modbus message received 246
249 9996 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 control block with
a write block with the following format.
Offset Description Length
0 9996 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.
Formatted Pass-Through Control Blocks
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 9996
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 this block
identification number. Ladder logic must handle the receipt of all Modbus write
functions to the processor and to respond as expected to commands issued by
the remote Modbus master device. The structure of the formatted pass-through
control block is shown in the following tables:
Function 5
Offset Description Length
0 0 1
1 9958 1
2 1 1
3 Bit Address 1
4 Data 1
5 to 248 Modbus message received 244
249 9958 1

ProSoft Technology MVI56-MCM Specifications

General

Brand	ProSoft Technology
Model	MVI56-MCM
Category	Cell Phone
Language	English