> On Jul 24, 2020, at 3:15 PM, Clem Cole <cl...@ccc.com> wrote:
>
>
>
> On Fri, Jul 24, 2020 at 2:37 PM Paul Koning <paulkon...@comcast.net
> <mailto:paulkon...@comcast.net>> wrote:
> The right answer would be a tweak to the console emulation in SIMH pdp11.
> Mumble... Paul - I'm not so sure. While DEC used MARK a lot, there were
> places that used EVEN parity a lot also on PDP-11's (Lord how, I hated 20 mA
> current loop ;-) at least by the time of widespread RS-232C interfaces it was
> glass ttys and usually a full 8-bit data path. 7-bit with odd/even is
> defined this way:
>
> bits of data
> (count of 1-bits) 8 bits including parity
> even odd
> 0000000 0 00000000 10000000
> 1010001 3 11010001 01010001
> 1101001 4 01101001 11101001
> 1111111 7 11111111 01111111
> FWIW: I'm on a Mac and I run a program called 'Serial' that can do that; but
> I thought most of the programs that simulate a serial connection for the
> different PC/Windows system have similar options. Certainly that was true
> when I did it with DOS.
I use minicom, and yes, it can do all those things. But that wasn't the case I
was thinking about. I thought the issue isn't so much the case where you have
a terminal emulator program talking to a serial port, but rather the case of
your command window in which you invoke simh (pdp11) and you're then talking to
the console terminal. I would rather not have to change the settings on my
regular shell to deal with oddball stuff expected by some application, I figure
that's the application's job.
> Anyway, I think the 'right' answer for simh is to ask the user to use a
> serial emulation program that can generate any of: 8-bit no parity, 7-bit no
> parity, or 7-bits of data plus an 8th parity bit with any of the 4 parity
> options: odd, even, mark (aways 1) or space (always 0). Seems to me, simh
> should bring 8 bits into the simulated serial port and let the SW running on
> the system decide what it's going to do with it.
>
> I'm curious to hear what Bob thinks?
Parity is something that comes in addition to the data. DEC UARTS (and many
others, I think) would let you set the data length (5, 6, 7, 8 bits) and the
parity setting (none, even, odd). So what you called "8 bits including parity"
is technically "7 bits with parity". If you set your UART for 8 bits with
parity, it would send 11 bits total: start, 8 data, parity, stop.
I've even run into 10-bit UARTs (on PLATO terminals). But that's not DEC stuff.
paul
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