exxos's Atari, Amiga & retro forum

While searching for suitable multiplexers for use with the ST cartridge, serial and ACSI ports it'll help to find out which specifications they must handle.
Does anyone have such info available for those ports (such as impedance, capacitance, voltage range and so on)?

I have no idea, but there you can find git sources:
- Cartridge device: https://github.com/sidecartridge/ataris ... berry-pico
- ACSI device: https://github.com/retro16/acsi2stm

The closest thing to that kind of documentation is probably this: "Engineering Hardware Specification of the Atari ST Computer System". The schematics and the datasheets for the specific chips that are connected to the ports would also be useful. You can get the documentation here:
https://docs.dev-docs.org/

But don't expect to get details about capacitance or impedance. And anyway, these parameters are going to vary wildly depending on the exact model and even board revision, let alone any add-ons or modifications. Voltage levels I can already tell you and they are pretty much industry standard. The Cartridge and the ACSI ports are compatible with TTL levels. The serial port is, at least in theory, +12V/-12V.

Cyprian wrote: 13 Jan 2025 21:27 I have no idea, but there you can find git sources:
- Cartridge device: https://github.com/sidecartridge/ataris ... berry-pico
- ACSI device: https://github.com/retro16/acsi2stm

I don't think those projects will provide much information about what the OP is asking.

ijor wrote: 14 Jan 2025 02:46 The closest thing to that kind of documentation is probably this: "Engineering Hardware Specification of the Atari ST Computer System". The schematics and the datasheets for the specific chips that are connected to the ports would also be useful. You can get the documentation here:
https://docs.dev-docs.org/

Excellent!
Thank you.

But don't expect to get details about capacitance or impedance. And anyway, these parameters are going to vary wildly depending on the exact model and even board revision, let alone any add-ons or modifications. Voltage levels I can already tell you and they are pretty much industry standard. The Cartridge and the ACSI ports are compatible with TTL levels. The serial port is, at least in theory, +12V/-12V.

Thanks. That info gets me at least started.
What I'm trying to do is create additional selectable outputs from the mentioned ports. A picture says more than words, so...
Here I will attach a C-Lab Export (which adds 3 extra MIDI OUT ports) to the serial port, but I also want the possibility to occasionaly be able to use the original serial port. Hence a multiplexer-based switch, controlled by a 2-position slide switch.

Similar in function to the above, here I will attach a Link '97 (ACSI to SCSI adapter) to the ACSI port, but in case I need to use the original ACSI port for something I want to switch over to that. Again, using a multiplexer-based switch, controlled by a 2-position slide switch

Yet, again similar to the others, but here I have several cartridge devices and dongles that don't necessarily work together in one long chain (actually I've confirmed that they don't).
So I've put the ones I need to work together in 4 "groups", and a multiplexer-based switch, controlled by a 4-position slide switch.

I've been told that I should use multiplexers suitable for the specific port, but having searched for this I've only found ones built for USB, HDMI etc. and not the "vintage" ones.
But if the values aren't critical (other than being able to handle the voltage limits of the signals in question), wouldn't it just be a matter of getting a MUX of the "analog switch" kind with enough individual switches (or combine several for the total number of signals the port has)?