July 1998
54AC191
Up/Down Counter with Preset and Ripple Clock
General Description
Features
n ICC reduced by 50%
The ’AC191 is a reversible modulo 16 binary counter. It fea-
tures synchronous counting and asynchronous presetting.
The preset feature allows the ’AC191 to be used in program-
mable dividers. The Count Enable input, the Terminal Count
output and the Ripple Clock output make possible a variety
of methods of implementing multistage counters. In the
counting modes, state changes are initiated by the rising
edge of the clock.
n High speed — 133 MHz typical count frequency
n Synchronous counting
n Asynchronous parallel load
n Cascadable
n Outputs source/sink 24 mA
n Standard Military Drawing (SMD)
— ’AC191: 5962-89749
Logic Symbols
Connection Diagrams
Pin Assignment
for DIP and Flatpack
DS100279-1
IEEE/IEC
DS100279-3
Pin Assignment for LCC
DS100279-2
Pin Names
CE
Description
Count Enable Input
DS100279-4
CP
Clock Pulse Input
P0–P3
PL
Parallel Data Inputs
Asynchronous Parallel Load Input
Up/Down Count Control Input
Flip-Flop Outputs
U/D
Q0–Q3
RC
Ripple Clock Output
TC
Terminal Count Output
™
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© 1998 National Semiconductor Corporation
DS100279
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