Re: Apple SSC and CTS/RTS choking on the 6551

[David.Empson@bbs.actrix.gen.nz]

In article <1992Nov20.210357.24001@mintaka.lcs.mit.edu> johnp@silver.lcs.mit.edu (John Palaima) writes:
> Does anyone know a hardware cure for fixing the screwy 6551 on the
> SSC card other than replacing it with the CMOS..it fixes the problem
> but the timing ould be too far off 

Please elaborate.  What do you mean by "the timing would be too far
off"?  The 6551 and 65C51 have nearly identical bus interface
timings characteristics.

I gather your problem with the 6551 is that CTS kills the trasmitter,
RTS kills the transmitter, DTR kills the receiver AND the transmitter,
and DCD kills the receiver.

On the 65C51, CTS still kills the transmitter, but it lets a partial
byte through.  Similarly, DCD kills the receiver but lets a partial
byte through.

The other signals behave as before - turning off RTS will disable the
transmitter, turning off DTR will disable all transmit and receive (and
interrupts).
-- 
David Empson

Internet: David.Empson@bbs.actrix.gen.nz    EMPSON_D@kosmos.wcc.govt.nz
Snail mail: P.O. Box 27-103, Wellington, New Zealand