[GreenKeys] Serial port FIFO issues

[John Nagle]

Jeff-1.0 (wa6fwi) writes:

> Side note: I ran across some free ware on a French website for talking 
> to the
> tty stuff, http://rxcontrol.free.fr/TTYTerm/index.html and as to be 
> expected, it
> has issues with communication via PCI based serial ports. I.e., sending the
> data in blocks rather than individual character. I did however at least 
> get some
> garbled text through the TU from the ITTY stream so it was good to see some
> results at last.

     That's an operating system configuration issue.  You need to turn off
the input and output FIFOs for very slow serial ports.  There's a built-in
accumulation timer with an accumulation time of 4 character times in most
serial ports.  For most baud rates, nobody notices, but at 45.45 baud,
that's more than half a second.  It's a Windows control panel option.

     This matters mostly if you're operating a Teletype in full-duplex
mode, with the computer doing the echoing.

					John Nagle