MVI56E-MCM ♦ ControlLogix Platform Reference
Modbus Communication Module User Manual
ProSoft Technology, Inc. Page 137 of 209
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 Blocks 9956 or 9957 from Processor to Module
This will inform the module that the command has been processed and can be
cleared from the pass-through queue.
Function 15
When the module receives a function code 15 while in pass-through mode, the
module will write the data using block ID 9959 for multiple-bit data. First the bit
mask clears the bits to be updated. This is accomplished by ANDing the inverted
mask with the existing data. Next the new data ANDed with the mask is ORed
with the existing data. This protects the other bits in the INT registers from being
affected.
Pass-Through Block 9959 from Module to Processor
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 9959 from Processor to Module
This will inform the module that the command has been processed and can be
cleared from the pass-through queue.
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