[Simh] pdp11 - console input with high bit set

[Johnny Billquist]

I would have to disagree with that. All older PDP-8 software is 
definitely using MARK parity, not EVEN. Both on input and output. 
(Sortof annoying if you aren't expecting it.)

The ASR33, as configured by DEC, was normally also set up with MARK 
parity, which is probably the reason all software expected it.

Actually, older PDP-11 software is also expecting MARK parity. Lots of 
the older diagnostics, for example.

I wouldn't know about older PDP-10 software, but it would be a little 
surprising if they did things differently than PDP-8 and PDP-11.

   Johnny

On 2020-07-24 19:26, Timothe Litt wrote:
> Actually, even parity was more common in the early daze of DEC async.  
> MARK always sets the high bit - even sets it only to make the total 
> number of 1s even.
> 
> Quick test: Given that #215 is CR - If the code is looking for #212 for 
> LF, it's mark.  If it's looking for #012, it's even.
> 
> Note also that the digits can also be used - e.g. '0' => 060 - is even, 
> while 260 would be Mark (or Odd).
> 
> Generating the expected format is a function of the terminal emulator.
> 
> On 24-Jul-20 04:37, Johnny Billquist wrote:
>> You need to have your terminal set to MARK parity.
>>
>>   Johnny
>>
>> On 2020-07-24 01:56, Paul Moore wrote:
>>> I am trying to run an RK11 diagnostic and am stuck.
>>>
>>> The diagnostic asks the user how many drives to test and I can get 
>>> the input to work
>>>
>>> Looking at the code, it is looking for digits and then cr.
>>>
>>> But it is actually looking for  #215, which is 0x8d. Which is CR with 
>>> the high bit set. (It also looks for #377 del with HB set)
>>>
>>> So what happens is that it just keeps reprompting
>>>
>>> I don’t see how that character ever gets into the system. I did ‘set 
>>> tti 8b’ but it made no difference. I can post the relevant code if 
>>> needed.
>>>
>>>
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>>
> 
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-- 
Johnny Billquist                  || "I'm on a bus
                                   ||  on a psychedelic trip
email: bqt at softjar.se             ||  Reading murder books
pdp is alive!                     ||  tryin' to stay hip" - B. Idol