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If any node on a Data Highway Plus network initiates multiple commands
(for example, the initiating node sets multiple bits at any time), the order
in which those commands get executed at the remote node cannot be
guaranteed. The initiating node, the network, and the receiving node
execute commands based on network conditions, including but not limited
to:
nodes buffering commands
retries due to noise on the network
If your application requires that commands be delivered in a specific order,
your logic must control the initiation of one command at a time on the
network and verify delivery before initiating additional commands. This
verification is completed by:
a done bit or an error bit in a PLC
a reply message in a computer
A done bit or a successful reply should cause the next command to be
initiated. If an error bit or a reply with non-zero status is returned, you
must decide the appropriate action based on your application.
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