ProSoft inRax MVI94-GSC-E, Руководство пользователя

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MVI94-GSC-E ♦ FLEX Platform Reference
Generic ASCII Comunication Module User Manual
Page 44 of 60
ProSoft Technology, Inc.
July 6, 2009
4.2.5 Data Flow between MVI94-GSC-E Module and Flex Processor
The following topics describe the flow of data between the two pieces of
hardware (Flex processor and MVI94-GSC-E module) and other devices
attached to the application port. The sections below show the three possible
types of communication devices that can be attached to the application port:
write-only, read-only and read-write.
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 MVI94-GSC-E module will never transmit data. All data received from the
device will be passed from the module to the Flex processor through the
module’s input image. Ladder logic in the processor must handle the data
received from the module. The output image on the module will only be used to
inform the module when the input image (read data) has been processed. This is
accomplished by copying the byte 0 in the input image to byte 0 of the output
image. The data flow diagram for a write-only device is shown below: