Datasheet

December 1990 5
Philips Semiconductors Product specification
Presettable synchronous 4-bit binary
up/down counter
74HC/HCT191
FUNCTION TABLE
TC AND RC FUNCTION TABLE
Notes
1. H = HIGH voltage level
L = LOW voltage level
I = LOW voltage level one set-up time prior to the LOW-to-HIGH CP transition
X = don’t care
↑ = LOW-to-HIGH CP transition
= one LOW level pulse
= TC goes LOW on a LOW-to-HIGH CP transition
OPERATING MODE
INPUTS OUTPUTS
PL U/D CE CP D
n
Q
n
parallel load
L
L
X
X
X
X
X
X
L
H
L
H
count up H L I ↑ X count up
count down H H I ↑ X count down
hold (do nothing) HXHXXno change
INPUTS TERMINAL COUNT STATE OUTPUTS
U/D CE CP Q
0
Q
1
Q
2
Q
3
TC RC
H
L
L
L
H
H
H
H
L
H
H
L
X
X
X
X
H
H
H
L
L
L
H
H
H
L
L
L
H
H
H
L
L
L
H
H
H
L
L
L
L
H
L
H
H
H
H
H
Fig.4 Functional diagram.