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

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: 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