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Signal Connections • 29

3.5 Timer / Counter Connection

The ACL-8112 has an interval 8254 timer/counter on board. It offers 3

independent 16-bit programmable down counters; counter 1 and counter 2

are cascaded together as a timer pacer trigger for A/D conversions and

counter 0 is free for user applications. Figure 3.10 shows the 8254

timer/counter connection.

Counter 0

Counter 1

Counter 2

CLK0

GATE0

OUT0

CLK1

GATE1

CLK2

GATE2

OUT1

OUT2

2MHz

Oscillator

Vcc

A/D Trigger

CN3 Pin-34

CN3 Pin-37

CN3 Pin-33

CN3 Pin-16

CN3 Pin-35

INT

EXT

8254 Timer/Counter

Figure 3.10 Block Diagram of 8254 Timer/Counter

The clock source of counter 0 can be internal or external, with the gate

being controlled externally and the output sent to CN3. As for counter 1

and counter 2, the clock source is internally fixed, while the gate can be

controlled externally and the output sent to CN3 too. All timer/counter

signals are TTL compatible.

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Adlink ACL-8112 Series Manual do Utilizador Página 37