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ProSoft Technology PLX31-EIP-SIE User Manual

Page 115

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PLX3x Series

MBTCP Protocol

Ethernet and Serial Gateways

User Manual

ProSoft Technology, Inc.

Page 115 of 218

September 17, 2014

A server device can, however, be forced into 'Listen Only Mode' in which it will
monitor the messages on the communications system but not respond to them.
This can affect the outcome of your application program if it depends upon any
further exchange of data with the remote device. Generally, the mode is forced to
remove a malfunctioning remote device from the communications system.

Sub-function Codes Supported
Only Sub-function 00 is supported by the gateway.

00 Return Query Data
The data passed in the request data field is to be returned (looped back) in the
response. The entire response message should be identical to the request.

Sub-function

Data Field (Request)

Data Field (Response)

00 00

Any

Echo Request Data


Example and State Diagram
Here is an example of a request to remote device to Return Query Data. This
uses a sub-function code of zero (00 00 hex in the two-byte field). The data to be
returned is sent in the two-byte data field (A5 37 hex).

Request

Response

Field Name

(Hex)

Field Name

(Hex)

Function

08

Function

08

Sub-function Hi

00

Sub-function Hi

00

Sub-function Lo

00

Sub-function Lo

00

Data Hi

A5

Data Hi

A5

Data Lo

37

Data Lo

27