On 15 Sep 97 at 16:26, David Wong wrote:

> I'm not that familar with Serial communications.  I'm trying to
> write code for a pic to communicate RS-485 to other serial devices.
> I'm confused on what the BRGH bit in the TXSTA register does.  I
> know that it selects between high and low speed.  But what
> constitutes high speed 19.2K, 38.4K, etc. what constitutes low speed
> 1200 baud, am I just really confused.  Could somebody please help.

Avoid it if you can, by using crystals that will let you use BRGH = 0
AND have good bitrate accuracy.

Trolling the list provided the following snippet -

> > The following commonly available crystal frequencies give you 0%
> > error on the common baud rates : 1.8432MHz, 2.4576 MHz, 3.6864 MHz, 4.9152
 MHz,  11.0592 MHz

You may get away with BRGH = 1, but MicroChip advises that errors may
occur with most of their chips, the 66,67,76,77 series excepted.  I'd
say if you aren't familiar with serial comms, then try and avoid one
more potential problem.
MikeS
<mikesmith_oz@nosp*m.relaymail.net>
(remove the you know what before replying)