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READ_VAR or WRITE_VAR does not re-establish communications after re-connecting cable.

Goals and Symptoms

READ_VAR or WRITE_VAR does not re-establish communications after re-connecting cable.

Causes and Fixes

The READ_VAR or WRITE_VAR does not re-establish communications after re-connecting the
Ethernet TCP/IP cable.

This will occur if the communications timeout is left at the default value of zero (0). A timeout value of
zero 0) will cause the function block to never timeout. This results in the The READ_VAR and
WRITE_VAR block to never close the TCP/IP connection when the Ethernet cable is disconnected
and re-connected. The PLC will need to be stopped and re-started after the Ethernet TCP/IP cable
is re-connected.

To resolve the issue, define a timeout value in the '%MW+2' management word of the READ_VAR
or WRITE_VAR block.

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