The 8253 Timer in the PC

D7 - D0

RD

WR

CS

A1

A0

CLK0

GATE0

OUT0

CLK1

GATE1

OUT1

CLK2

GATE2 is connected to bit 0 of Port B of an internal 8255. Using IO.EQU this can be accessed as PCCHB

OUT2 is connected to bit 5 of Port C of an internal 8255. Using IO.EQU this can be accessed as PCCHC.

1.19 MHz clock

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