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74F169
Unit Loading/Fan Out
Functional Description
The 74F169 uses edge-triggered J-K type flip-flops and
has no constraints on changing the control or data input
signals in either state of the clock. The only requirement is
that the various inputs attain the desired state at least a
setup time before the rising edge of the clock and remain
valid for the recommended hold time thereafter. The paral-
lel load operation takes precedence over other operations,
as indicated in the Mode Select Table. When PE
is LOW,
the data on the P
0
–P
3
inputs enters the flip-flops on the
next rising edge of the clock. In order for counting to occur,
both CEP
and CET must be LOW and PE must be HIGH;
the U/D
input then determines the direction of counting.
The Terminal Count (TC
) output is normally HIGH and goes
LOW, provided that CET
is LOW, when a counter reaches
zero in the Count Down mode or reaches 15 for the
74F169 in the Count Up mode. The TC
output state is not a
function of the Count Enable Parallel (CEP
) input level.
Since the TC
signal is derived by decoding the flip-flop
states, there exists the possibility of decoding spikes on
TC
. For this reason the use of TC as a clock signal is not
recommended (see logic equations below).
1. Count Enable
= CEP • CET • PE
2. Up: (74F169): TC = Q
0
• Q
1
• Q
2
• Q
3
• (Up) • CET
3. Down: TC = Q
0
• Q
1
• Q
2
• Q
3
• (Down) • CET
Mode Select Table
H = HIGH Voltage Level
L = LOW Voltage Level
X = Immaterial
State Diagram
Pin Names Description
U.L.
Input I
IH
/I
IL
HIGH/LOW
Output I
OH
/I
OL
CEP Count Enable Parallel Input (Active LOW) 1.0/1.0 20 µA/−0.6 mA
CET
Count Enable Trickle Input (Active LOW) 1.0/2.0 20 µA/−1.2 mA
CP Clock Pulse Input (Active Rising Edge) 1.0/1.0 20
µA/−0.6 mA
P
0
–P
3
Parallel Data Inputs 1.0/1.0 20 µA/−0.6 mA
PE
Parallel Enable Input (Active LOW) 1.0/1.0 20 µA/−0.6 mA
U/D
Up-Down Count Control Input 1.0/1.0 20 µA/−0.6 mA
Q
0
–Q
3
Flip-Flop Outputs 50/33.3 −1 mA/20 mA
TC
Terminal Count Output (Active LOW) 50/33.3 −1 mA/20 mA
PE CEP CET U/D
Action on Rising
Clock Edge
L X X X Load (P
n
→ Q
n
)
H L L H Count Up (Increment)
H L L L Count Down (Decrement)
H H X X No Change (Hold)
H X H X No Change (Hold)
