PLC-5, ControlNet, and Flex I/O Frustration

I will try to make this as concise as possible. I had to add a 1794-IB16/A and a 1794-OB16P/A to an existing ControlNet Flex I/O network. The processor is a PLC-5/40C,1.5. I powered down the Flex rack adapter, added the modules to the rack, and then downloaded a new ControlNet configuration with the new modules added to the configuration. Since these were discrete modules I didn't think there would be any further configuration needed. However after going back to run mode, my new input module would work but the output module would not. Tried another module thinking perhaps the first one was defective. Still would not work. After spending an hour or so trying to find documentation that would explain how to do this, we somehow stumbled across a configuration screen in the scanlist configuration that has to do with Rack Specifications. The existing modules had "Include in Input" Yes, "Include in Output" Yes. The modules I had just added both had no for Input and Output. After changing these to yes and downloading the new configuration both new modules started working. Later I again tried to find documentation that explained this but I still could not. I even found technote 43653 on the AB knowledgebase that supposedly explains the process for adding discrete modules. According to this article all you have to do is make sure the input and output sizes are as big or bigger than the slots you are going to use. The input and output sizes for this Flex rack were both set to 8. When I contacted AB support about this they said they could find no documentation related to the "Include in Input/Output" configuration. I have used Flex I/O on Remote I/O and ethernet before but this was my first experience with ControlNet.

Maybe a new technote will come from this that will help someone else in the future.

Thanks.

There is always one more rathole hidden in the walls.