Help concurrent polling on HC11

[windozeuser]

I am doing a class project on the HC11 and I need to poll a keypad and the UART which is connected to a wireless receiver. The problem is I need to poll these both pretty much at the same time, how can I do this without having them conflict with each other? I'm not allowed to use interrupts since we didn't learn them in the course.

 

[3v0]

Should not be hard to do. I expect the UART has a bit you can check. You did not say if you were sending data both ways with the UART. I will just show the case for sending the keypad data to the radio.

repeat
  if(key_pad_pressed)  then
       wait_for_uart_tx_done  // do not overrun the uart tx buffer
       send key
  end_if
// put rx code here if needed
end_repeat