🚀 go-pugleaf

In article <1991Feb18.185444.7021@uhura.neoucom.EDU> wtm@uhura.neoucom.EDU (Bill Mayhew) writes:

   The recieving end is typically a dedicated 8741 or simialr
   ROM-bearing microprocessor that decodes the keystrokes and presents
   the keystrokes to the BIOS through an interrupt drivien routine.

   much in concert.  For instance, the BIOS in my '386 at home is
   American Megatrends (AMI) and so is the sticker over the quartz
   window on the keyboard controller (think in my case it is an 8741
   uP).  It is left as an exercise for the reader to contact AMI to
   find out what, if anything, is available.

Progress is wonderful :-)  Seems like newer machines have dedicated
keyboard controllers, then. I have schematics of IBM's original XT. 
The 'keyboard controller' on the mother board consists of glue chips.

Roughly, there's a 9 bit shift register, and when the 9th bit gets a
'1', it freezes clocking to the shift register, and interrupts the
CPU. The CPU reads the byte using PA0-7 of the 8255 peripheral 
controller, then resets the chain, using yet another bit of 8255, 
so that the next character can be received. 

Note that the keyboard itself has a microcontroller, in IBM's case
an 8048. 

/ Jon Sreekanth

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