Reference MVI69E-MBS ♦ CompactLogix Platform
User Manual Modbus Serial Enhanced Communication Module
Page 140 of 154 ProSoft Technology, Inc.
June 28, 2017
7.4.16 Pass-through Formatted Block for Function 15 (9959)
Block 9959: Pass-Through Formatted Block for Function 15
When the module receives a function code 15 in Pass-Through mode, the
module writes the data using block ID 9959 for multiple-bit data. First the bit
mask clears the bits to be updated. This is accomplished in RSLogix 5000 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. This function can
only be used if the Block Transfer Size parameter is set to 120 or 240 words.
Block 9959: Request from Module to Processor
Bit mask to use with the data set. Each bit to be considered with the data set has
a value of 1 in the mask. Bits to ignore in the data set has a value of 0 in the
mask.
Where n = 60, 120, or 240 depending on the Block Transfer Size parameter.
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 a write
block with the following format.
Block 9959: Response from Processor to Module
This informs the module that the command has been processed and can be
cleared from the Pass-Through queue.
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