ProSoft Technology MVI71-GSC - Manual (Page 59)

Reference MVI71-GSC ♦ PLC Platform
Generic Serial Communication Module
ProSoft Technology, Inc. Page 59 of 82
January 31, 2008
When the side-connect interface is used, word 80 of the configuration file is used
for the same purpose. To perform the warm-boot operation, place a value of
9998 in this location. To perform a cold-boot operation, place a value of 9999 in
this location.
5.1.10 Data Flow between MVI71-GSC Module and PLC Processor
The following topics describe the flow of data between the two pieces of
hardware (PLC processor and MVI71-GSC module) and other devices attached
to the application ports. Each application port on the module is configured
independently to interface with serial communication devices. The sections below
show the three possible types of communication devices that can be attached to
the application ports: write-only, read-only and read-write. All examples display
the BTR/BTW interface but equally apply to the side-connect interface.
Write-Only Devices
Write-only devices are those that only send data to the module. An example of
this type of device is a barcode reader. The reader is programmed to only send
data and is not expected to receive data. In this configuration, the application port
on the MVI71-GSC module will never transmit data. All data received from the
device will be passed from the module to the PLC processor through the
module's BTR blocks. Ladder logic in the processor must handle the data
received from the module. The BTW blocks will only be used to inform the
module when the BTR image has been processed. This is accomplished by
copying the word 0 value in the BTR block to word 0 of the BTW block. The data
flow diagram for a write-only device is shown below: