Richard,
did you try to connect 2 serial ports of the same cpu to see if they works?
If they work I would investigate a gnd loop or gnd voltage difference
problems.
Surely to understand where is the problem you would understand if there
are wrong data
or missing data. Start a New Thread

[cut]
> You shouldn't have a problem receiving at 3mbaud with well written
service code - assuming you set
> the fifo trigger at 14 bytes, you should get an interrupt about
every 46uS, i.e. about every 2200
> instructions at 48MHz. Shouldn't take more than a couple of hundred
instruction timess to service
> the int.

I wouldn't set the fifo trigger at 14 bytes at this rate. You would
have to starting servicing the interrupt at 2 character times before
the fifo is full, which can be tricky if you have other interrupts or
badly behaving code (long interrupt disable sequences). IMHO 8 bytes
is a good compromise.

The FIQ is a good choice at this rate, anyway. Start a New Thread