ProSoft Technology MVI71-MCM - Manual (Page 56)

MVI71-MCM ♦ PLC Platform Reference
Modbus Communication Module
Page 56 of 111 ProSoft Technology, Inc.
December 28, 2007
On power up the module begins performing the following logical functions:
1 Initialize hardware components
o
Initialize PLC backplane driver or side-connect drivers
o
Test and Clear all RAM
o
Initialize the serial communication ports
2 Determine the interface to the backplane (side-connect or block transfer).
3 Wait for Module Configuration from PLC processor
4
Initialize Module Register space
5 Enable Slave Driver on selected ports
6 Enable Master Driver on selected ports
After the module has received the Module Configuration Block from the
processor, the module will begin communicating with other nodes on the
network, depending on the configuration.
5.2.2 Main Logic Loop
Upon completing the power up configuration process, the module enters an
infinite loop that performs the following functions:
Call I/O Handler
Call CFG/DEBUG Port
Driver
Call Network Master &
Slave Drivers
Call I/O Handler
Transfers data between the module and processor
(user, status, etc.)
Call Serial Port Driver
Rx and Tx buffer routines are interrupt driven. Call to
serial port routines check to see if there is any data
in the buffer, and depending on the value, will either
service the buffer or wait for more characters.
Call Network Master & Slave Drivers
Generate messages and
respond to messages received.
From Power Up Logic
5.2.3 PLC Processor Not in Run
Whenever the module detects that the processor has gone out of the Run mode
(that is, Fault or PGM), the Modbus ports can be shut down as prescribed in the
user configuration. When the processor is returned to a running state, the module
will resume communications on the network.