26 Feb
2006
26 Feb
'06
12:11 p.m.
would it be accurate to say that a unit, such as my
Mindset II, which has the power switch built into the
keyboard turns the system on by asserting the
power-good signal (when the switch is activated)? I
Unlikely, if you're talking about a conventional PC. The Power-good line
is an output from the PSU, it's used to reset the CPU until the power
lines have all come up.
If you want to be able to turn the machine on/off, presumably you need a
special PSU with either some kind of relay (solid-state or
electromechanical) in the mains input circuitm or some way to shut the
chopper circuit down.
I would also expect at least one 'alwyas on' output.
know from the Byte article that an 8042 supervises
the
keyboard (same or similar to the IBM PC/AT). I was
The 8042 is a microcontorller. It can be programmed to do almost
anything.
It might even be powered all the time, and control the rest of the PSU
via one of its output port lines. In which case the power on/off switch
might send a keycode to the main unit, the 8042 would detect this and
control the PSU appropriately.
Do you even know that the keyboard connecotr is the same as on a PC? Is
it possible there's an extra pin dedicated to the power on/off control?
Rememebr the PC keyboard connector has 5 pins, but one of them was almost
never used (if's officially a reset output from the PC).
thinking I could tie something? to +5 volts in an
attempt to determine if my pos even works. And how far
is it from reality to suggest all pc kbs are the same
except for their 8048/9/8748/9 programming?
If by 'PC' you mean IBM compatible, well all clone keyboards should lookl
the same to the host computer (byt be warned I've found bugs here!). Anny
differences in the microcontroller program would be to handle a
difference electical layout of the keys.
-tony