[Simh] PDP-8 KL8E XON/XOFF

[Johnny Billquist]

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