The D-25 PTR / PTP parallel interfaces are TTL, the ones I have had on the bench at any rate, typically using 74 series for interfacing and 5V rails. Generally, the data lines are on pins 1 to 8 after that it gets a bit YMMV and at the top end you get ground and exported voltage. Hence my Dostek's emulator is a good guide comment. Additionally, the pin out does not mimic what must be the later D-25 PC printer plug layout.
An additional confounding factor is that PTR/PTP are substantially from the era when D-25 connectors were commonly used for RS232 serial comms, and quite a few featured serial interfaces : RTFM territory. +/- 12V levels were used for RS232 back in the day, these days a MAX3232 on 3v3/LVTTL with integral charge pumps for +/- 6v is typical. And of course RS-423, RS-422 and RS-485 are all potentially applicable interface circuit standards; however only RS-485 is not in the legacy category Numeric gloup Martin -----Original Message----- From: Jon Elson via cctalk [mailto:cctalk@classiccmp.org] Sent: 16 May 2024 22:20 To: Martin Bishop via cctalk <cctalk@classiccmp.org> Cc: Jon Elson <el...@pico-systems.com> Subject: [cctalk] Re: Papertape-Reader Decitek 442A9: need manual/schematics On 5/16/24 15:15, Martin Bishop via cctalk wrote: > Micha > > That the board is TTL and 2 layer by the look of it makes reverse engineering > rather more tractable : good luck. > > The 25p D pin outs for readers/punches seem substantially > standardised, I believe the standard is RS-323 (all search attempts assume you mean RS-232). The logic levels are 12 V or so, so not quite TTL compatible. Jon
