[Simh] PDP-8 KL8E XON/XOFF

[Mark Pizzolato]

Hi Johnny,

The fundamental issue Bill is seeing is a problem in the simh code and not the hardware or the host OS.  There may be a hardware issue, but I doubt it and if there is, the simh issue will have to be addressed first.

- Mark

On Monday, June 6, 2016 at 9:01 AM, Johnny Billquist wrote:
> On 2016-06-06 17:44, William Wuttke wrote:
> > Hi Mark,
> >
> > Looking at the sources, the latest date on most of the files is Dec 15, 2015.
> >
> > The serial port is actually 2 GPIO pins on the Broadcom SOC chip, levels
> translated to RS-232 via a MAX3232.
> >
> > The Raspberry Pi is a model 1 B+.
> >
> > I looked at the sources online, and I saw the work done on the serial port
> speed on the input side, but nothing on the output side.
> >
> > The deal is that unless you are using ancient hardware connected to
> simh/PDP-8, you wouldn’t notice any problem.
> >
> > I wanted to post to this mailing list first to get some ideas before I create an
> issue.
> 
> Your problem is that the serial port on your raspberry is buffering for
> you. Either in the hardware, or else in the device driver.
> 
> The PDP-8 should not output data at the bps rate of the serial port. A
> real machine don't do that. However, a real KL8E or KL8JA only have a
> one character buffer. You need simh to simulate this then. but how to do
> that might be very difficult, since this buffering is happening on the
> hardware, or device driver in the OS for the serial port, and is not
> something simh have real control over, or deep access to.
> 
> 	Johnny
> 
> --
> 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
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