8 Jun
2010
8 Jun
'10
2:11 p.m.
On 8 Jun 2010 at 20:13, Tony Duell wrote:
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
some "autoswitching" (XT-AT mode) keyboards that will send out a
continuous stream of wrong-parity ACKs until they receive either an
XT-style reset (holding clock and data low for ~200 msec) or an AT
response (porobably any command; NAK or RESET will do).
It goes without saying that bizarre and wonderfully non-functional
things happen if you plug an XT keyboard into an AT-or-better system
or an AT keyboard into an XT system.
--Chuck