Of course this depends on the quality of your signal.

This thread has got me to thinking, and coding, and I am pretty sure I've
come up with a way to get 4 in and 4 out at 31250buad on a PIC18CXX2 at 10
MIPS. The trick involves accumulating input samples on each channel and
processing them 5 at a time instead of one-by-one. This idea was inspired by
byte-at-a-time CRC algorithms. Basically you end up with a monster state
machine, about 70 states, with 32 (ie: 2^5) possible inputs for each state.
The state machine is then stored as one whopping big (about 8K) table. But
hey, what's 8K when you've got 32K on chip? :-)

Bob Ammerman
RAm Systems
(high function, high performance, low level software).

----- Original Message -----
From: Alan B Pearce <A.B.Pearce@RL.AC.UK>
To: <PICLIST@MITVMA.MIT.EDU>
Sent: Sunday, May 28, 2000 7:04 AM
Subject: Re: [PIC]: [EE]: Microcontroller with 4 USARTs


> >Unfortunately, to receive you need to run your interrupt handler somewhat
> >faster than the bit time.  I have successfully built a software UART
using a
> >interrupt 6x of the bit rate. I expect 5x would work pretty well.
>
> You get away with 4 samples per bit time if you are not doing it
synchronous to
> the bit edges. Many years ago before high speed async modems were commonly
> available we used to send async data through synchronous modems, and could
do it
> with no errors if the async baud rate was a quarter of the sync modem
rate.