Ray:
The Dallas data sheet for the DS80C320 does a horrible job of describing the operation of the serial port interrupts. Actually it is horrible at describing many SFR functions of the chip. There is a separate document called the "High-Speed Microcontroller Users Guide" which does a little bit better job.

I took a quick look and what I see is in Mode 3 the interrupt on transmit should come on just after the last bit is sent out. On receive the interrupt in inhibited unless the 9th bit is set to '1'. I guess the idea is to use the mode 3 till you are satisfied that you are addressed in the other 8 bytes, and then switch the serial port over to mode 2 while you receive your packet. Then flip back to mode 3 awaiting the next packet addressing framing.

I can email this Users Guide to you if you cannot locate it in the WEB. I recall it took some effort to find it!! It is a 1.16 MByte PDF document of some 175 pages. If you are interested just drop me a line at mkaras@CarouselDesign.com.


Michael Karas