"Thomas C. Sefranek" wrote:
> I think I found a BUG in the 16C73...  See if you agree?

It's not a bug. It behaves as expected/documented.

> The Peripheral Interrupt Register #1  (PIR1) has a value of  0000 0000
> on Power up.
> BUT!!!! Bit 4 (TXIF) is a 1 if the USART transmit buffer is empty!

Well, TXREG -IS- empty, just as the doc says.

> Does bit 4 being a 0 at power up indicate the buffer is full?

No, it means that the USART hasn't been turned on yet.

> If so, who filled it?  (And when will it empty?)
> if not, why is bit 4 a 0?

TXREG started out empty. Turning on the USART (SPEN) turns on TXIF
so that it will generate an interrupt and get loaded.

Robert