Int E0 Fn 0012  - Pcrobots V1.41 - "receive" - Get Data From Other Robots  [g]

   AX = 0012h

Return: AX = status
       0000h no data available
       0001h data retrieved
       BX = sender's ID
       CX = data

Note:  each robot has a 20-word receive FIFO; if the FIFO is full, other
     robots will be unable to send more data until some is read