Philips pm2521 - Page 134

142
74LS161
4-BIT
BINARY
COUTER
PIN CONFIGURATION
MR
[T
¥]Vcc
CP
[y
TC
Do
[I
i3
Qo
0i
\T
nlQi
D2
H"
u]
Qj
03
[ll
1T]Q3
CEP
\2_
1^
CET
GND
[F
PE
LOGIC
SYMBOL
9
3 4 5
6
MODE
SELECT-FUNCTION TABLE
OPERATING
Inputs
Outputs
MODE MR CP
CEP CET
PE
D
n
Q
n
TC
Reset
(Clear) L X
X X
X X
L L
Parallel Load
H t X
X
1
1 L L
H t X X
1 h
H
(b)
Count
H
t
h h
h(d)
X
count
(b)
Hold
(do
nothing) H X 1(c)
X
h(d) X
Qn
(b)
H
X
X 1(c)
h(d)
X
Q
n
L
H
=
HIGH
voltage
level
steady state
L
=
LOW
voltage
level steady
state
h
=
HIGH voltage
level one
setup time
prior
to
the LOW-to-HIGH
clock transition
1
=
LOW
voltage
level one setup time prior to the LOW-to-HlGH
clock transition
X
=
Don't
care
Q
=
Lower case
letters indicate the state of
the referenced output
prior
to the
LOW-to-
HIGH
clock transition
f
=
LOW-to-HIGH
clock transition