PS2 Keyboard Interface

.James Zou.
10/25/2010
PS2 Keyboard Interface will disappear soon. However, in the computer history, as one of the main input tool ever, the PS2 keyboard played a very important role. I designed a virtual keyboard many years ago so I understood the ps2 keyboard interface. I will show you how to read the wave form  between the 8042 and the keyboard, then I will list the initial communication sequence of the keyboard initialization. For those who want to know more detail about the PS2 keyboard interface, please read the IBM’s technical reference manual.

(1) When keyboard sends command to the host, the wave form should like the following picture:


               Red: host is driving. Blue: Keyboard is driving. Data is valid at rising edge.
(2) When the host sends command to keyboard, the wave form should like the following picture:

Blue: keyboard is driving. Data is valid at falling edge.
Keyboard inialization sequence:
Host –> KB: FF
KB –> Host: FA AA  00
Host –> KB: F2
KB –> Host: FA 00
Host –> KB: F3
KB –> Host: FA
Host –> KB: 0A
KB –> Host: FA
Host –> KB: F2
KB –> Host: FA 00
Host –> KB: E8
KB –> Host: FA
Host –> KB: 00
KB –> Host: FA
Host –> KB: E6
KB –> Host: FA
Host –> KB: E9
KB –> Host: FA
KB –> HOST: 90
KB –> Host: 02
KB –> Host: C8
Host – KB: E8

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About superjameszou

Hardware Design Engineer
This entry was posted in PS2 Keyboard & Mouse Debugging. Bookmark the permalink.

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