VM600 networking manual MAVM600-NET/E 9 - 7
Edition 9 - February 2018
Error handling
SETTING UP A MODBUS CONNECTION (CPUM SW VERSION 071 OR LATER)
9.3.1 Communication errors
The latest implementation of the VM600 Modbus server provides an additional error
exception code:
• If the client (master) requests information from a VM600 card that is unplugged, the
exception code “06” will be returned. This code traditionally indicates a slave device busy
error exception response. (The master should retransmit the message later when the
slave is available again.)
NOTE: When an error occurs, the server (slave) returns a message response that includes
an exception code. To distinguish between the message request and message
response, the MSB (most significant byte) of the function code is set to “1” in the
message response.
NOTE: Attempts to communicate with (access) an unplugged card will result in the
following communication error: the exception code “06” will be returned.
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