Well, I'm not sure why yet, but when I switched to to using channel b, everything is working fine there. So, I guess it'll take a bit more work to figure out what's going on with that, but at least it's working.

You're making it unnecessarily difficult for yourself by "jerking around" this way. The data table and method of loading the 28L92's registers I earlier put up does work—the code is right out of my POC V1.2 firmware. It would be easier to help you if you were to post the entire code you are using rather than little unconnected bits and pieces. Post it as a text file and I'll take a look.

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x86?  We ain't got no x86.  We don't NEED no stinking x86!

This thread is starting to sound eerily similar to the problems I had with the 28L92 in my build last year, where for some reason the wrong baud rate table is selected, and so instead of 115.2k bps I was getting 9600 bps. I never did figure it out, and in fact the problem persists even after a complete rebuild (including new breadboards, a different 28L92, and a different PLC44->DIP44 adapter). I ended up just using 38.4 kbps since it's the same on all baud rate tables.

One thing I never did try is port B...my build is on hold right now while I work on an automation project for the house,but once it's back on the bench I may have to give port B a shot.