0

After yesterday's Windows 10 update and reboot, BIOS hung before booting. As it turned out it's something with the keyboard. Still I'm unsure whether it's the keyboard (only 30 years old ;-)) or the PS/2 on-board connector. Hard to believe that a Windows update killed my hardware, but anyway:

Noticing that all three keyboard LEDs were flashing three times after a reset, I wonder whether the keyboard wanted to tell me something: Are there any common LED-indicated (pattern of flashing) keyboard self-test results?

Improve this question
1
  • As a matter of fact, it seemed to be a software problem (like the keyboard being crashed): After a lengthy power-off phase the keyboard worked again. Before I had interrupted power too, but obviously not long enough to discharge all capacitors.
    – U. Windl
    Commented Jan 5, 2021 at 8:31

1 Answer 1

Reset to default
0

As nobody did answer, here is what I found (The PS/2 Keyboard Interface):

At power-on or software reset ("Reset" command) the keyboard performs a diagnostic self-test referred to as BAT (Basic Assurance Test). When entering BAT, the keyboard enables its three LED indicators, and turns them off when BAT has completed (so they flash once for about 0.5s).

The host may send a command to the keyboard, e.g.:

  • 0xFF (Reset) - Keyboard responds with "ack" (0xFA), then enters "Reset" mode (See above).

So observing the three LEDs flash three times seemed to indicate that the host sent a reset to the keyboard three times (and then probably gave up for an unknown reason).

I also found M17x and M15x LED Error Codes LED Error Codes that indicates that the system BIOS may use the keyboard LEDs to signal a system error.

Improve this answer

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .