PDP-8/e

[Josh Dersch]

On Fri, Dec 7, 2018 at 11:10 PM Rod G8DGR via cctalk <cctalk at classiccmp.org>
wrote:

> I’m sure that would work  but I only have an 8650  110 baud only card
> Rod
>

The M8650 does a wide variety of baud rates.   See here:
https://homepage.divms.uiowa.edu/~jones/pdp8/hard8e/kl8e.html

- Josh



>
>
> Sent from Mail for Windows 110 baud
>
> From: Bob Rosenbloom via cctalk
> Sent: 08 December 2018 03:41
> To: cctalk at classiccmp.org
> Subject: Re: PDP-8/e
>
> On 12/7/2018 7:01 PM, Pete Turnbull via cctalk wrote:
> > On 07/12/2018 17:44, Jon Elson via cctalk wrote:
> >> On 12/07/2018 11:22 AM, systems_glitch via cctalk wrote:
> >>> Indeed, unless you need character pacing.
> >>>
> >>>
> >> Actually, with the correct settings of the serial port (xon/xoff or
> >> CTS pin) the serial port driver should do this, too, so cat would work.
> >
> > A PDP-8/E doesn't have a CTS pin and the loaders don't support
> > XON/XOFF, though.
> >
> The PDP-8 needs to control the serial CTS function. This was called
> reader-run when using a Teletype machine. FOCAL won't load without it.
> You can modify the serial card (mine was an M8655) to support the
> function. Here's what I did:
>
> Cleaned up from Aaron Nabil's and Lyle Bickley's write up.
>
>   Hack the M8655 to support reader-run by mapping it to RS-232 hardware
> flow control.
>
> 1. Cut the trace leading from Pin 1 of E54 (a 7400).  This is the input
> that clears the Reader Run FF when a new character starts to come in.
>
> 2. Jumper from Pin 1/E54 to Pin 3/E38, a spare gate on a 7400 that we
> are going to use an inverter.
>
> 3. Tie Pin 1 and Pin 2 of E38 together, and run them to Pin 20 of E19,
> the UART.
>      This supplies the signal to the reader-run FF that tells it that
> it's got an incoming character and to de-assert the reader-run line.
>      Normally this is tied to the current loop receiver, we've just
> moved it to the UART so any received data will clear the FF.
>
> 4. Cut a ground traces on 4 of E50, a 1488 RS-232 transmitter. This is
> what would normally supply the continuously asserted RTS (and DTR) signal.
>
> 5. Jumper from pin 7 of E39, a 7474 flip-flop to pins 4 of E50. E39 is
> the "reader-run flip-flop".  Now RTS follows the reader run signal.
>
> Bob
>
> --
> Vintage computers and electronics
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>