SUMMARY of: True ttya/ttyb pinouts? (xmit clock)

From: Matt Crawford (
Date: Sat Nov 16 1991 - 11:58:30 CST

According to (who else?) Hal Stern, the manuals are indeed wrong in
calling pin 15 of the CPU serial ports an output. It's an input.
And by my own experiment, if the serial chip is told to take the
transmit clock from its TRxC* pin, it will get the clock from pin 15.
Making only that change reduced the loss rate for "spray" packets
through my homemade SDLC driver from 22.5% to 0.0% for packets from
86 to 300 bytes. Two observatories are happy now. :-)

I'm only working at 9600 bps here, so I guess the modem and the
sparcstation were just enough apart in frequency ...
Matt Crawford Astronomy & Astrophysics U of Chicago

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