74HC161 pdf datasheet

MM74HC160 Synchronous
Decade Counter with Asynchronous Clear
MM54HC161/MM74HC161 Synchronous
Binary Counter with Asynchronous Clear
MM54HC162/MM74HC162 Synchronous
Decade Counter with Synchronous Clear
MM54HC163/MM74HC163 Synchronous
Binary Counter with Synchronous Clear
General Description
The MM54HC160/MM74HC160, MM54HC161/
MM74HC161, MM54HC162/MM74HC162, and
MM54HC163/MM74HC163 synchronous presettable counters
utilize advanced silicon-gate CMOS technology and internal
look-ahead carry logic for use in high speed counting
applications. They offer the high noise immunity and low
power consumption inherent to CMOS with speeds similar
to low power Schottky TTL. The 'HC160 and the 'HC162 are
4 bit decade counters, and the 'HC161 and the 'HC163 are
4 bit binary counters. All flip-flops are clocked simultaneously
on the low to high transition (positive edge) of the CLOCK
input waveform.
These counters may be preset using the LOAD input. Presetting
of all four flip-flops is synchronous to the rising edge
of CLOCK. When LOAD is held low counting is disabled and
the data on the A, B, C, and D inputs is loaded into the
counter on the rising edge of CLOCK. If the load input is
taken high before the positive edge of CLOCK the count
operation will be unaffected.
All of these counters may be cleared by utilizing the CLEAR
input. The clear function on the MM54HC162/MM74HC162
and MM54HC163/MM74HC163 counters are synchronous
to the clock. That is, the counters are cleared on the positive
edge of CLOCK while the clear input is held low.
The MM54HC160/MM74HC160 and MM54HC161/
MM74HC161 counters are cleared asynchronously. When
the CLEAR is taken low the counter is cleared immediately
regardless of the CLOCK.
Two active high enable inputs (ENP and ENT) and a RIPPLE
CARRY (RC) output are provided to enable easy cascading
of counters. Both ENABLE inputs must be high to
count. The ENT input also enables the RC output. When
enabled, the RC outputs a positive pulse when the counter
overflows. This pulse is approximately equal in duration to
the high level portion of the QA output. The RC output is fed
to successive cascaded stages to facilitate easy implementation
of N-bit counters.
All inputs are protected from damage due to static discharge
by diodes to VCC and ground.