DEC VT05 with OS/8 -- basic system rebuild?
vrs at msn.com
Mon May 18 13:46:32 CDT 2009
From: "Tony Duell" <ard at p850ug1.demon.co.uk>
>> (And to make it clear: hardware flow control is definitely not possible
>> towards a PDP8)
> 'Nothing is impossible except skiing through a revolving door' :-)
> More seriously,. I would have thought you could make hardware
> modifications ot the serial interface PCB, possibly to gate ome of the
> ready signals with the flow control input. Or (in this case), detect the
> CR (or is it LF that's the problem?) and then hold the ready line
> deasseted either for enough time for the VT05 to complete its operation
> or until it gets some ecternal acknowledge signal.
> No, I am not suggesting this is a sensible solution to the problem,but it
> is _possible_
Someone suggested a microcontroller to kludge up a flow control signal
from the VT05 earlier.
Once such a signal is derived (however that is done), the 8/i, 8/L, and
PDP-12 *do* have a TTL signal input that will perform this function.
There isn't a single "serial interface PCB", however. There's one for
input, one for output, another for the baud rate generator, and another
yet for the current-loop interface. They are connected together by the
custom wire-wrap "backplane". So you'd need to convert the flow control
signal to a TTL level, then apply it to the magic wire-wrap post on
The nice thing is that it could be done with minimal, reversable mods to
the vintage gear.
(Somebody else mentioned Reader-Run -- that doesn't come into it, as
that handles flow control in the other direction.)
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