I've been prototyping a circuit that connects two 16550 Serial UARTs to a
PIC (the PIC16F877).  I know the PIC already has a UART, but I'm using that
already.  I was thinking about doing some bit banging to eliminate the
external UARTs, but in my application I need the speed and accuracy of these
external UARTS.

Ok, so now my problem.
For some reason, when I assert the Read line on the UART (to tell the uart
to put it's recieved byte onto the bus), it takes almost a full second for
the bus to arrive at the correct value.  On top of that, the _RXRDY line
(which indicates when a byte is waiting to be read) does not de-assert when
I'm done reading.  Unfortunately, I don't have a scope to see what's going
on, so I can't say for certain how deep this problem is.

I've worked with the 16550 UART in this manner before and it worked fine.
Could I have melted the 16550's bus drivers or something?

I'm using PORTD of the PIC as my data bus, and the 6 bits of PORTA for
control (yes, I have a pull-up resistor on RA4)

If nothing obvious comes up, I can post the scematics or code.

Thanks,

Mike

--
http://www.piclist.com#nomail Going offline? Don't AutoReply us!
email listserv@mitvma.mit.edu with SET PICList DIGEST in the body