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IN74ALS161AD

Synchronous 4 Bit Counters; Binary, Direct Reset

Integral Corp. 

TECHNICAL DATA

IN74ALS161A

Synchronous 4 Bit Counters; Binary,

Direct Reset

This synchronous, presettable counter features an internal carry

look-ahead for application in high-speed counting designs.

Synchronous operation is provided by having all flip-flops clocked

simultaneously so that the outputs change conicident with each other

when so instructed by the count-enable inputs and internal gating.

This mode of operation eliminates the output counting spikes that

are normally associated with asynchronous (ripple clock) counters. A

buffered clock input triggers the four flip-flops on the rising (positive-

going) edge of the clock input wave form.

This counter is fully programmable; that is the outputs may be

preset to either level. As presetting is synchronous setting up a low ORDERING INFORMATION

level at the load input disables the counter and causes the outputs to

IN74ALS161AN Plastic

agree with the setup data after the next clock pulse regardless of the

IN74ALS161AD SOIC

levels of the enable inputs.

TA = -10° to 70° C for all

The carry look-ahead circuitry provides for cascading counters for

packages

n-bit synchronous applications without additional gating. Instrumental

in accomplishiing this function are two counter-enable inputs and a

ripple carry output. Both countenable inputs (ENABLE P and

ENABLE T) must be high to count, and ENABLE T is fed forward

PIN ASSIGNMENT

to enable the ripple carry output. The ripple carry output thus

enabled will produce a high-level output pulse with a duration

approximately equal to the high level portion of the QA output. The

high-level overflow ripple carry pulse can be enable successive

cascaded stages. Transitions at the ENPor ENT are allowed

regardless of the level of the clock input.

• Internal Look-Ahead for Fast Counting

• Carry Output for n-Bit Cascading

• Synchronous Counting

• Synchronously Programmable

• Load Control Line

• Diode-Clamped Inputs

LOGIC DIAGRAM

PIN 16 =VCC

PIN 8 = GND

1

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