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2

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,

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

3. Down: TC

= Q

Mode Select Table

H

= HIGH Voltage Level

L

= LOW Voltage Level

X

= Immaterial

State Diagram

Pin Names

Description

U.L.

HIGH/LOW

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

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

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

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)