PRE

CLK

D

CLR

Q

Q

C

C

C

C

C

C

C

C

C

C

TG

TG

TG

TG

SN54HC74, SN74HC74

SCLS094E – DECEMBER 1982 – REVISED DECEMBER 2015

www.ti.com

8 Detailed Description

8.1 Overview

Figure 3 describes the SNx4HC74 devices. As the SNx4HC74 is a dual D-Type positive-edge-triggered flip-flop

with clear and preset, the diagram below describes one of the two device flip-flops.

8.2 Functional Block Diagram

Figure 3. Logic Diagram (Positive Logic)

8.3 Feature Description

The SNx4HC74 inputs accept voltage levels up to 5.5 V. Refer to the Recommended Operating Conditions for

appropriate input high and low logic levels.

8.4 Device Functional Modes

Table 1 lists the functional modes of the SNx4HC74.

Table 1. Function Table

INPUTS

OUTPUTS

PRE

CLR

CLK

D

Q

Q

L

H

X

X

H

L

H

L

X

X

L

H

L

L

X

X

H

H

↑

H

H

L

H

H

↑

L

L

H

H

H

L

X

(1)

This configuration is nonstable; that is, it does not persist when PRE or CLR returns to its inactive

(high) level.

10

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