9

Sequence:

1. Load (preset) to binary thirteen.

2. Count up to fourteen, fifteen, zero, one, and two.

3. Inhibit.

4. Count down to one, zero, fifteen, fourteen, and thirteen.

FIGURE 10. CD74AC191 DECODE COUNTERS TYPICAL LOAD, COUNT, AND INHIBIT SEQUENCES

FIGURE 11. SYNCHRONOUS N-STAGE COUNTER WITH PARALLEL GATED TC/RC

FIGURE 12. SYNCHRONOUS N-STAGE COUNTER USING RIPPLE TC/RC

LOAD

PRESET

INPUTS

P0

P1

P2

P3

CLOCK

DOWN/UP

ENABLE

Q0

Q1

Q2

Q3

TERMINAL COUNT

RIPPLE CLOCK

LOAD

H

L

13 14 15

0

1 2

COUNT UP

INHIBIT

COUNT DOWN

2

2

1

0

15 14

13

L

L

L

L

L

H

H

H

H

H

H

U/D

CE

CP

TC

U/D

CE

CP

TC

U/D

CE

CP

TC

DIRECTION

CONTROL

ENABLE

CLOCK

U/D

CE

CP

RC

U/D

CE

CP

RC

U/D

CE

CP

RC

DIRECTION

CONTROL

ENABLE

CLOCK

CD74AC191, CD74ACT191