ML1400 to ML1400 messaging

Hello,
I am trying to send descrete I/O data between 2 Micrologix 1400 PLC's using messaging instructions. Can anyone tell me if I have to use an entire word of data for each individual I/O point that I'm sending or if there is a better way to share this type of data between 2 ML 1400's?

You could message one or more INTs, use individual bits for your data, and have some bits remaining for whatever else comes up.

If you’re messaging physical I/O data, you could copy a block of status bits and have more data available in case it’s useful.

Yes, you must message at least whole integers. If I need to exchange two bits, I will block off ten integers for the message. You will need spares and you can't online edit the rung with the MSG instruction in a Micrologix. If you reserve plenty of spares, you may never need them, but if you don't do that you certainly will need them and it will be at a moment where interrupting the PLC will be costly.

The overhead for an Ethernet message to transport just one integer is going to account for the bulk of the over the wire traffic, so making the packet bigger by a few bytes will have minimal impact on the network.

5618 said:

You could message one or more INTs, use individual bits for your data, and have some bits remaining for whatever else comes up.

If you’re messaging physical I/O data, you could copy a block of status bits and have more data available in case it’s useful.

Click to expand...

got it. Thanks for the good advice! I appreciate it.