9 Jun
2010
9 Jun
'10
12:55 p.m.
On 8 Jun 2010 at 20:13, Tony Duell wrote:
That is not the same thing at all. The serial command/data transfer
to/from the system is bit-banged by the microcontroller, so the
microcontroller must be running its firmware correctly to handle that
RESET command. Yes there is such a command which initialises various
parameters of the keyboard, but it's not what I was thinking of.
I was thinking of the hardware reset to the microcontroller that causes
it to run the firmware in the first place. The reset pin of the 8048 is
connecvted to an RC network in the keyboard, not to the hardware reset
signal in the host system (strangely, at least on XT machines, pin 3 of
the DIN connector (labelled as 'reserverd') did carry the system reset
line, but no IBM keyboard used it. I don't think it's connected at all in
AT machines.
If the microcontroller does not reset properly, then it will not be able
to accept any commands from the host.
-tony
The keyboard contains a microcotroller (8048
IIRC) which is reset by
an RC network in the keybaord, it doesn't sue the system reset line. i
suppose if the 5V line was risingtoo slowly, then the microcontroller
may not initialise properly.
If it's connected to an AT+ system said PC normally sends out a RESET
command to the keyboard. This is pretty much required as there are