MC14526B(2000) データシートの表示（PDF） - ON Semiconductor

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MC14526B
(Rev.:2000)

Presettable 4-Bit Down Counters

ON Semiconductor 

MC14526B

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.

VSS (Pin 8) — The most negative power supply potential.

This pin is usually ground.

VDD (Pin 16) — The most positive power supply

potential. VDD may range from 3 to 18 V with respect to VSS.

STATE DIAGRAM

MC14526B

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