[Simh] pdp11 - console input with high bit set

[Mark Pizzolato - Info Comm]

On Friday, July 24, 2020 at 11:36 AM, Paul Koning wrote:
> > On Jul 24, 2020, at 2:28 PM, David Gesswein <djg at pdp8online.com> wrote:
> >
> > On Fri, Jul 24, 2020 at 06:12:17PM +0000, Paul Moore wrote:
> >> Not helped by not knowing what KSR really means.
> >>
> >
> > Keyboard send receive. A model 33 teletype without paper tape.
> > ASR was the model with paper tape, Automatic send receive.
> >
> > DEC used teletype's that generated mark parity. From the manuals
> > keyboards were available to generate other parity. A reasonable amount
> > of old code for PDP-8's assumed mark parity. Later code ignores the upper
> bit.
> >
> > I thought the high bit setting would be turned off if you used set tti
> > 7b or 8b but never verified.
> 
> 7b, yes.  But that only helps with software that sets the top bit on output, as
> some old Unices do.  It doesn't help with the problem Paul M raised, which is
> software that insists on mark parity input.
> 
> The right answer would be a tweak to the console emulation in SIMH pdp11.
> I wonder if this was done for PDP8 and not PDP11 because it was known to
> be needed on the one but people hadn't run into it for the other.

The console emulation in simh actually has functionality to present input data 
with different character sizes and/or parity.   Leveraging this functionality is 
missing from the PDP11 console devices.  I will fix this over the next day or so.

- Mark