Operating instructions

Reference PTQ-MCM ♦ Quantum / Unity Platform
Modbus Communication Module
ProSoft Technology, Inc. Page 107 of 139
April 29, 2008
The following flow chart show the implementation of the direct pass-thru block:
Is the
destination
address
valid?
Attempt to write command
to backplane queue.
Send response with
Invalid Address exception.
Is there an
available
space in the
queue?
Y
N
Add to backplane
command queue.
Send response with Slave
Busy exception.
Y
N
Send normal response.
Receive write
command.
Wait for next
command.
The following modbus commands are accepted during direct pass-thru operation:
Function
Code
Description Code Maximum Count Quantum Memory Area
6 Preset Single Register 1 4x (holding register)
16 Preset Multiple Registers 125 4x (holding register)
The destination address where the data will be copied at the processor is
calculated as: the module will add 40001 to the destination address received.