undefined | Better HN

0 points0xmarcin4y ago0 comments

PS/2 is a two way protocol. If Keyboard sends data it, then it controls the clock. If Host sends data then it will take care of the clock signal.

From my limited electronics experiencence, you need a pull-up resistors when connecting TTL ICs to CMOS ICs.

0 comments

2 comments · 1 top-level

bogantech4y ago· 1 in thread

It is two way, but the clock is always provided by the keyboard.

PS/2 devices all have pull-up resistors as the only thing driving the lines high are those resistors.

The mcu on either side only ever pull it low and never high.

http://www.lucadavidian.com/2017/11/15/interfacing-ps2-keybo...

userbinator4y ago

Then perhaps IBM's keyboards somehow push the clock closer to the limit (16.7kHz, I believe) than motherboards' controllers can handle? Unfortunately I wasn't able to find any measurements of different keyboards' clock frequencies.

j / k navigate · click thread line to collapse