[Simh] pdp11 - console input with high bit set
Paul Moore
paulmoore100 at hotmail.com
Fri Jul 24 19:39:37 EDT 2020
I have hacked the TTUF_KSR flag here
uptr->buf = sim_tt_inpcvt (c, TT_GET_MODE (uptr->flags)|TTUF_KSR);
in pdp11_stddev.c
and this works, (its what the pdp8 console has) but obviously this isn’t the correct solution, but it gets me unblocked.
-----Original Message-----
From: Simh <simh-bounces at trailing-edge.com> On Behalf Of Mark Pizzolato - Info Comm
Sent: Friday, July 24, 2020 4:34 PM
To: Paul Koning <paulkoning at comcast.net>; David Gesswein <djg at pdp8online.com>
Cc: Simh at trailing-edge.com
Subject: Re: [Simh] pdp11 - console input with high bit set
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
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