Congratulations! Step by step...
Here's a simple way to test your serial I/O hardware. Write a program that reads EF3 (or whatever flag bit you are using for serial input, and echoes it to Q (or whatever you are using for serial output). Something like:
0000 3603 If EF3 pin is high,
0002 7B Set Q
0003 3E05 If EF3 pin is low,
0005 7A Reset Q
0006 3000 Branch to start
1802 clock speed and baud rate don't matter. Any key you type on your terminal keyboard should be echoed back to your display. This verifies that things are hooked up correctly.
If it doesn't work, try swapping the Set Q and Reset Q instructions.
Excellence does not require perfection. -- Henry James
Lee A. Hart http://www.sunrise-ev.com