Reference MVI56E-GSC/GSCXT ♦ CompactLogix or MicroLogix Platform
User Manual Enhanced Generic ASCII Serial Communication Module
Page 78 of 140 ProSoft Technology, Inc.
April 24, 2017
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 which has been configured to only send
data and is not expecting to receive data.
In this situation, the application port on the MVI56E-GSC module will never have
to transmit data. All data received from the barcode reader will be passed from
the module to the ControlLogix 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 has been processed. This is accomplished by copying the Byte 499
in the input image to Byte 0 of the output image.
The data flow diagram for a write-only device is shown below:
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