MC14526B

http://onsemi.com

2

FUNCTION TABLE

Inputs

Output

Resulting

Function

Clock Reset Inhibit

Preset

Enable

Cascade

Feedback

“0”

X

X

X

H

H

H

X

X

X

L

H

X

L

L

H

L

H

H

Asynchronous reset*

Asynchronous reset

Asynchronous reset

X

L

X

H

X

L

Asynchronous preset

L

L

L

H

L

L

X

X

L

L

Decrement inhibited

Decrement inhibited

H

H

L

L

L

L

L

L

L

L

L

L

L

L

L

L

L

L

L

L

No change** (inactive edge)

No change** (inactive edge)

Decrement**

Decrement**

X = Don’t Care

NOTES:

** Output “0” is high when reset is low, only if CF is high and count is 0000.

PIN DESCRIPTIONS

Preset Enable (Pin 3) — If Reset is low, a high level on the

Preset Enable input asynchronously loads the counter with

the programmed values on P0, P1, P2, and P3.

Inhibit (Pin 4) — A high level on the Inhibit input pre−

vents the Clock from decrementing the counter. With Clock

(pin 6) held high, Inhibit may be used as a negative edge clock

input.

Clock (Pin 6) — The counter decrements by one for each

rising edge of Clock. See the Function Table for level

requirements on the other inputs.

Reset (Pin 10) — A high level on Reset asynchronously

forces Q0, Q1, Q2, and Q3 low and, if Cascade Feedback is

high, causes the “0” output to go high.

“0” (Pin 12) — The “0” (Zero) output issues a pulse one

clock period wide when the counter reaches terminal count

(Q0 = Q1 = Q2 = Q3 = low) if Cascade Feedback is high and

Preset Enable is low. When presetting the counter to a value

other than all zeroes, the “0” output is valid after the rising

edge of Preset Enable (when Cascade Feedback is high). See

the Function Table.

Cascade Feedback (Pin 13) — If the Cascade Feedback

input is high, a high level is generated at the “0” output when

the count is all zeroes. If Cascade Feedback is low, the “0”

output depends on the Preset Enable input level. See the

Function Table.

P0, P1, P2, P3 (Pins 5, 11, 14, 2) — These are the preset

data inputs. P0 is the LSB.

Q0, Q1, Q2, Q3 (Pins 7, 9, 15, 1) — These are the

synchronous counter outputs. Q0 is the LSB.

This pin is usually ground.

STATE DIAGRAM

MC14526B

4

3

2

1

0

15

14

13

12

11

10

9

8

7

6

5