SIO/2  UART  Poll  3

 <=Poll 2                                                                                                                                           Interrupts =>

On the previous pages we:

 - set up the environment constants  

 - included Interrupt redirects               

 - configured the Write registers

Now we'll add the assembly code to configure just channel A to receive and transmit data.

PC16C550 UART vs. SIO/2 UART

In the 16550, the Line Status Register (LSR) has two bits that we focus upon:

 - Bit 0: Data Available

 - Bit 5: Transmit Holding Register is Empty

The equivalent SIO/2 bits in Read Register 0 (RR0) are:

 - Bit 0: Rx Character Available

 - Bit 2: Tx Buffer Empty

SIO/2 UART polling mode: Receive & Transmit Configuration

<=Poll 2                                                                                                                                                             Interrupts 1 =>