Ports 60H-63H are decoded by the PC's 8255A Programmable Peripheral
Interface chip.  These ports control the keyboard and timers and contain
configuration information collected during the POST.

Port  Description
060H  Read keyboard:
IN   al,60H  ;fetches most recent scan code.   See INT 09H
AT keyboard data register.                     See AT Keyboard
(Note: AT Keyboard register duplicated at port 64H)

061H  PPI port B.
 7 6 5 4 3 2 1 0 
                  bit mask
                  0: 01H gate timer channel 2 to speaker
                  1: 02H pulse speaker 1=out, 0=in
                     (see Speaker Control for examples)
                  3: 04H 1=read high switches;
                         0=read low ones (see 62H)
                  4: 10H 0=enable RAM parity checking; 1=disable
                  5: 20H 0=enable I/O channel check
                  6: 40H 0=hold keyboard clock low
                  7: 80H 0=enable keyboard; 1=disable keyboard

062H  PPI port C.
 7 6 5 4 3 2 1 0 
       0 equipmt 
                  0-3: DIP switch values.     See Equipment List
                    5: 1=Timer 2 channel out
                    6: 1=I/O channel check
                    7: 1=RAM parity check error occurred.

See Also: Speaker Control
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Programmable Peripheral Interface (PPI) Ports