Maximum Baud Rate error tolerance

[BigWumpus]

...in the good old days, a UART (8250) uses a clock of 16-times (?) the baudrate. So ist can sample the signal feg. at the middle of die time.

What is about saying:
1/8 of a bit jitter in 10 bits ? (8N1)
It would be 1,25% error.

I think it belongs to the intelligence (!) of the receiver to take the best samplepoints inside a serial character.

Modern PICs are able to get very close baudrate by using higher frequencies and bigger dividers.

If you are using an PIC-PIC-conversion, you are able to define your own baudrate by using "good" dividers of a standard frequency.

[Luciano]

Hi Keith,

Use a baud rate friendly crystal. (0% baud rate error).

18.432 MHz for the 18F452 and 3.6864 MHz for the 16F88s.
Does your compiler support these oscillator frequencies?

Best regards,

Luciano

* * *

Baud rate friendly crystals:

1.8432 MHz
3.6864 MHz
7.3728 MHz
11.0592 MHz
14.7456 MHz
18.4320 MHz

[keithdoxey]

Use a baud rate friendly crystal. (0% baud rate error).

18.432 MHz for the 18F452 and 3.6864 MHz for the 16F88s.
Does your compiler support these oscillator frequencies?

Baud rate friendly crystals:

1.8432 MHz
3.6864 MHz
7.3728 MHz
11.0592 MHz
14.7456 MHz
18.4320 MHz

Hi Luciano,

According to the PBP manual the only supported frequencies are
Oscillator speed in MHz: 3(3.58) 4 8 10 12 16 20 24 25 32 33 40 so any timing function would be off. I could compensate for this but it would make my IR timing routines more complicated.

As I said at the start, if BOTH PICs are off by the same amount then it wouldnt matter if it was 50% as they would be running at the same speed.

My question was more out of curiosity as to how far out you could get before comms would be unreliable.

Thanks to everyone for the replies