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DVP-ES2/EX2/SS2/SA2/SX2/SE Operation Manual - Programming
Exception response:
The PLC is expected to return a normal response after receiving command messages from the master
device. The following table depicts the conditions that either a no response or an error response is
replied to the master device.
1. The PLC did not receive a valid message due to a communication error; thus the PLC has no
response. The master device will eventually process a timeout condition.
2. The PLC receives a valid message without a communication error, but cannot accommodate it,
an exception response will return to the master device. In the exception response, the most
significant bit of the original command code is set to 1, and an exception code explaining the
condition that caused the exception is returned.
An example of exception response of command code 01H and exception 02H:
Sent message:
Field Name ASCII Hex
STX : 3A
Slave Address 01 30 31
Command code 01 30 31
Starting Address Hi 04 30 34
Starting Address Lo 00 30 30
Number of Points Hi 00 30 30
Number of Points Lo 10 31 30
Error Check (LRC) EA 45 41
END CR LF 0D 0A
Feedback message:
Field Name ASCII Hex
STX : 3A
Slave Address 01 30 31
Function 81 38 31
Exception Code 02 30 32
Error Check (LRC) 7C 37 43
END CR LF 0D 0A
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