"Richard Clark" wrote in message
...
Which is no more complex than setting 4 register bits - I wouldn't
call that a "routine," however.
-- I've
even written a few. :-)
Why more than one? Were the rest undersampling routines?

These were software RS-232 receivers, so you make use of whatever timers, edge
interrupts, etc. that you have sitting around to first the start bit, load up
a timer to then trigger in (what should be) the middle of the bit time for the
sample, etc. I've written pretty much the same routines a small handful of
times on different CPUs and in different languages.

The first ones I wrote were on ~1MIP CPUs in assembly and were limited to
about 2400bps full-duplex if you were also trying to run a reasonably
responsive terminal emulator (e.g., wanted to still have 50% of the CPU
available for the emulator), whereas more recently I've written them on ~20MIP
CPUs in C and can easily do 9600bps full-duplex with only a small impact on
CPU usage.

---Joel