Omega-engineering OME-A8111 Uživatelský manuál stáhnout pdf (Strana 22)

2.6 8254 Timer/Counter

The 8254 Programmable timer/counter has 4 registers from Base+0 through Base+3. For

detailed programming information about 8254, please refer to Intel‘s “Microsystem

Components Handbook”. The block diagram is as below.

Cin: clock input

Cout: clock output

INTCLK: internal clock

Cin

Gate

Cout

Counter 0

Cin

Gate

Cout

Counter 1

Cin

Gate

Cout

Counter 2

INTCL

VCC

10K

PACER CLK

Counter0, counter1 and counter2 are all 16 bit counters. Counter 1 and counter 2 cascade

as a 32-bit timer. The 32-bit timer is used as a pacer timer.

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