PiDP-8 – The Teletype Connexion

For a Model 33 Teletype machine to be used with the PiDP-8 as a console device, a few things need to be done (this also applies generally to simh/PDP-8):

• You need a current loop to RS-232 converter (self-powered).
• If not using the PiDP-8 serial port, you need a USB to RS-232 adapter that will work at 110 baud.
• For proper “PDP-8” operation, you need to strap the Model 33 for MARK parity. This is covered in the Teletype documentation which is available online.
• In simh, you need to “set TTI 8B” and “set console serial=<device>;110-8n2”, where <device> is either the actual device, e.g., /dev/ttyUSB0, or the simh serial device, e.g., ser0.
• You need to ensure that the OS/8 KL8E device handler is compiled with “emulate tab” support. (Tabs on the teletype are not supported.)
• If a Model 33 ASR using the paper tape reader, you need to modify the Low Speed Paper Tape device handler to increase the between-byte timeout.