On Fri, Dec 7, 2018 at 11:10 PM Rod G8DGR via cctalk <cctalk@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@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 > www.dvq.com > www.tekmuseum.com > www.decmuseum.org > > >