Operating instructions

Reference PTQ-MCM ♦ Quantum / Unity Platform
Modbus Communication Module
ProSoft Technology, Inc. Page 99 of 139
April 29, 2008
Master Specifications
A port configured as a virtual Modbus Master device on the PTQ-MCM module
actively issues Modbus commands to other nodes on the Modbus network. One
hundred commands are supported on each port. Additionally, the master ports
have an optimized polling characteristic that polls slaves with communication
problems less frequently. The Quantum processor can be programmed to control
the activity on the port by actively selecting commands from the command list to
execute or issuing commands directly from the ladder logic.
8.2 Functional Overview
8.2.1 Backplane Data Transfer
The current version of the PTQ-MCM backplane driver (version 2.10 or newer),
uses a Large I/O model, which differs from previous versions of the backplane
driver in that it transfers all of the data in the Read and Write databases between
the module and the processor on every scan.
The [Backplane Configuration] section of the configuration file defines the starting
registers for read and write operations, as well as the number of registers to use
for each data area.
[Backplane Configuration]
Failure Flag Count : 0 #
Error/Status Block Pointer : 3000 #Number of register to store error and
#status
The values in the example configuration file section above are illustrated in the
following diagram.
Processor
PTQ Module
Database
40001 to
40064
Words 1 to 64
Command Control
30001 to
30064
Words 1 to 64
Command Control
Words 65 to 164
Holding Register
(Write area)
Words 65 to 164
Input Register
(Read area)
40065 to
40164
30065 to
30164
0
500
99
599
Read Data
Write Data