ProSoft Technology MVI94-MCM-MHI User Manual
Page 80
Reference
MVI94-MCM ♦ Flex I/O Platform
User Manual
Serial Communications Modbus Communication Module
Page 80 of 109
ProSoft Technology, Inc.
March 29, 2011
Block Response from Module to Processor
Word Offset
Description
0
This word contains the block 2001 to 2006 requested by the processor.
1
This word contains the next read request block identification code.
2
This word contains the number of commands in the block placed in the command
queue.
3
Not used.
4
Not used.
5
Not used.
6
Not used.
The ladder logic can examine word 2 of the input image to determine the number
of commands placed in the command queue. Any errors associated with the
command can be viewed in the command list error table.
Transferring the Command Error List to the Processor
You can transfer the command error list to the processor from the module
database. To place the table in the database, set the Command Error Pointer
parameter to the database location desired.
To transfer this table to the processor, make sure that the Command Error table
is in the database area covered by the Read Data.
Pass-Through Blocks (9956 to 9958, 9960)
When the port is configured as a slave with pass-through, Modbus write
commands 5, 6, and 22 that are addressed to the slave will be passed across the
backplane for processing by the ladder logic. Due to their length, Modbus write
commands 15, 16, and 23 will have their data written to the database in the same
manner as no pass-through mode. The module must complete the block
transfer before it can accept another pass-through write command. The first
word contains the block identification number indicating the type of command
received. The second contains the length of the data in words being written
across the backplane. The third word contains the destination address from the
write command. The fourth contains the data. If floating-point is enabled and the
data comes from a floating-point register, the fourth word will contain the first
word of the data and the fifth word will contain the second word of data.