Bruce Cannon wrote:

>Hello:
>Reading the specs for 12Cxx, looks like calibrated osc value can vary nearly
>+-500kHz.  Has anyone used these parts (with internal osc) for serial comm,
>and if so, how?
>

        Certainly! We've had good results using '508 devices with 9600 baud
comms that rely on the internal oscillator for timing. Our measurements
show that it's pretty good at normal temps and ~5V Vdd.
        To reduce timing errors though, keep transmissions short (stick to
8N1, and preferrably 8N2 if you can afford the time). With 8 data and 1
start and even 5% timing error, you're only looking at 45% total error. By
receiving or sending only a few bytes at a time, the receivers have a
chance to reset and errors don't accumulate. A 256bit block would likely be
impossible to send reliably.


        Jim Nagy
        Elm Electronics
  ICs for Experimenters
http://www.elmelectronics.com/