Controller and memory card identification

[MasterLink]

This may be one of the silliest questions, or perhaps it's not silly at all, but after looking over the pinout of the memory and controller ports, and seeing how they are wired here: https://www.consolesunleashed.com/files ... 36x506.png

I'm left stumped, if they all share the same SPI bus, how on earth can the PS1 know which port a controller or memory card is actually inserted in?

Before asking I was actually keen on trying out my new DSO's ability to decode an SPI bus and poke around for some reverse engineering (and probably will still even with an answer as I need to get acquainted with my new DSO after using a Tektronix 2236 for....ever actually) and see how they talk to each other, but I figured I'd ask first since I'm sure there's an obvious answer I'm just missing here.

[gwald]

https://problemkaputt.de/psxspx-control ... quence.htm