74HC161 4Bit Binary Counter Async Reset 74161

Description
The ’HC161, ’HCT161, ’HC163, and ’HCT163 are
presettable synchronous counters that feature look-ahead
carry logic for use in high-speed counting applications. The
’HC161 and ’HCT161 are asynchronous reset decade and
binary counters, respectively; the ’HC163 and ’HCT163
devices are decade and binary counters, respectively, that
are reset synchronously with the clock. Counting and
parallel presetting are both accomplished synchronously
with the negative-to-positive transition of the clock.
A low level on the synchronous parallel enable input, SPE,
disables counting operation and allows data at the P0 to P3
inputs to be loaded into the counter (provided that the
setup and hold requirements for SPE are met).
All counters are reset with a low level on the Master Reset
input, MR. In the ’HC163 and ’HCT163 counters
(synchronous reset types), the requirements for setup and
hold time with respect to the clock must be met.
Two count enables, PE and TE, in each counter are
provided for n-bit cascading. In all counters reset action
occurs regardless of the level of the SPE, PE and TE inputs
(and the clock input, CP, in the ’HC161 and ’HCT161
types).
If a decade counter is preset to an illegal state or assumes
an illegal state when power is applied, it will return to the
normal sequence in one count as shown in state diagram.
The look-ahead carry feature simplifies serial cascading of
the counters. Both count enable inputs (PE and TE) must
be high to count. The TE input is gated with the Q outputs
of all four stages so that at the maximum count the terminal
count (TC) output goes high for one clock period. This TC
pulse is used to enable the next cascaded stage.
NOTES:
1. The TC output is High when TE is High and the counter is at Terminal Count (HHHH for HC/HCT161 and ’HC/HCT163).
2. The High-to-Low transition of PE or TE on the ’HC/HCT161 and the ’HC/HCT163 should only occur while CP is HIGH for conventional
operation.
3. The Low-to-High transition of SPE on the ’HC/HCT161 and SPE or MR on the ’HC/HCT163 should only occur while CP is HIGH for
conventional operation.