54AC191
Up/Down Counter with Preset and Ripple Clock
General Description
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.
Features
n I
CC
reduced by 50%
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
Pin Names Description
CE Count Enable Input
CP Clock Pulse Input
P
0
–P
3
Parallel Data Inputs
PL Asynchronous Parallel Load Input
U/D Up/Down Count Control Input
Q
0
–Q
3
Flip-Flop Outputs
RC Ripple Clock Output
TC Terminal Count Output
Connection Diagrams
FACT™ is a trademark of Fairchild Semiconductor Corporation.
DS100279-1
IEEE/IEC
DS100279-2
Pin Assignment
for DIP and Flatpack
DS100279-3
Pin Assignment for LCC
DS100279-4
July 1998
54AC191
Up/Down
Counter
with
Preset
and
Ripple
Clock
© 1998 National Semiconductor Corporation DS100279 www.national.com