S100 serial card problems redux

All: As posted previously, I've been having problems getting a Solid State Music card to work with my Altair. The background is that I want to get Microsoft BASIC running on it but the working serial card (a VG Bit Streamer card) cannot be configured to work with BASIC without patching BASIC. So, I've spent the last two weeks performing various tests. Here are the results: Working: 8800b with Vector Graphics Bit Streamer single serial I/O card. 8251 based. Using modified Turnkey Monitor program with actual I/O routines Non-working: same system but using a Solid State Music serial card which is based on the AY-3-1015 (or equivalent) UAR/T. No working sample code provided in the manual but configuration instructions for status bit location and polarity is easily followed (a few jumpers and swapping an LS368 for an LS367). So I created three test cases, two that are considered "Altair Revision 1" compatible by the manual and one that makes the AY3-1015 look like an 8251. I also wrote a serial loopback program to echo characters back. None of these cases work. Now here's what I noticed last night. When running the Bit Streamer card (the working configuration), the INP light is illuminated on the front panel. OK, makes sense. In the non-working configurations, the INP light is dark. So, I single-stepped the code and the right 8080 opcode is being executed. Based on this one would have to say that something's wrong with the SSM card on the input side, except for the fact that I thought that the INP status was generated by the CPU. To further complicate things, sending random characters to the serial port from the computer works -- I get characters on the screen. Any thoughts? Rich