Gavin Jackson wrote:
>
> Hi there
>
> I am using the BSF instruction to set bits
> on PORTD on a 16c74A. The whole port is
> configured as output (CLRF TRISD). The
> problem is, when I set a bit on the port, any
> other bits that were set, clear and then the
> bit the instruction specifies, sets.
> Why don't the other bits remain set?
>
> I also had a problem getting the serial port
> on the 16c74A to work. I tried everything!
> It turned out the 2.4576MHz crystal was
> not quite accurate enough. One would think
> that crystals were supposed to be quite
> accurate.
Can't answer your PortD problem, I use mine for muxed address/data so I
only output bytes to it.  I have had no problems with the UART and I use
a 2.4576MHz crystal, too.  Even with BHRG low (note the silicon bug),
you should be able to get bang-on baud rates at 38,400 (SPBRG==0),
19,200 (SPBRG==1) and lower.  I use 9600 (SPBRG==3) and 1200 (SPBRG==31)
with no problem.  (I can't directly vouch for 19.2 and 38.4, but they
should be fine.)

Bottom line: make sure that you've got BHRG low.  Otherwise, look to
your code because baud rates should be fine even at +/- 10% -- that
would be a *really* flaky crystal.

--Matt