> I know nothing about the IDC2, but I *do* know that an RC-osc
> will have a hard time to give you any relailable serial 
> communication.
> You need *some* crystal (or maybe resonator) based osc to be able
> to use the UASRT (or maybe the prec internal osc block on newer 
> devices).

You need about 50/N% clock stability overall for async operation. 
better is better.
So for 1+8+1=10 bits you need 50/10%=5% accuracy.

If your PC end crystal is approaching 0% in error then you get most of 
that 5% at the microprocessor end. Some (but by no means all) RC 
clocks will give you that sort of accuracy across voltage, temperature 
and time.

But, as Jan-Erik says, something better than RC is a really good idea 
if you can manage it. A resonator is fine.

If you aren't at all sure what your baud rate is then Murphy says it's 
almost certainly wrong.
(If you ARE sure then Murphy says it may be wrong :-) ).

If you have a scope then the shortest bit length will tell you what 
the baud rate is if you send anything with a 010 or 101 sequence in 
it.

No scope?
Set data to, say, $00, with a good gap between bytes.
If you can send individual characters without CRLF it's ***MUCH*** 
easier to work out what's happening.
If you are sending slower than you think then the receiving routine 
will see an $00 followed by a second character with b0xxxxxxx. ie 
01111111 or 00111111 or 00011111 etc depending how slow. if reaaally 
slow it will se several $00's followed by a b0xxxxxxx.
Having your PC end able to display the result of receiving $00 helps a 
lot here :-)

So, if you send 1 character from the uP and see several characters, 
odds are it's too slow. Double sending data rate and try again?
See $00 - it works.
Still see 2+ characters, double clock rate again.

If you are sending faster than you think the PC will see N 0's and M 
1's / 1<=N<=7, M=8-N.
Decode the displayed character and you can see how much faster it is 
than you expected.

Using a scope is much easier.




        RM 

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