specification will result in excessive power consumption and could cause oscillations. More details can be found

in the Implications of Slow or Floating CMOS Inputs application report.

Do not leave TTL-compatible CMOS inputs floating at any time during operation. Unused inputs must be

terminated at VCC or GND. If a system will not be actively driving an input at all times, a pull-up or pull-down

resistor can be added to provide a valid input voltage during these times. The resistor value will depend on

multiple factors; however, a 10kΩ resistor is recommended and typically will meet all requirements.

6.4 Device Functional Modes

Table 6-1 lists the functional modes of the CDx4AC(T)164.

Table 6-1. Function Table

INPUTS(1)

FUNCTION

A

B

CLR

CLK

X

X

L

X

Shift register is cleared.

L

X

H

↑

First stage of the shift register goes low.

Other stages store the data of previous stage, respectively.

X

L

H

↑

First stage of the shift register goes low.

Other stages store the data of previous stage, respectively.

H

H

H

↑

First stage of the shift register goes high.

Other stages store the data of previous stage, respectively.

(1)

H = High Voltage Level, L = Low Voltage Level, X = Do Not Care

CD54AC164, CD74AC164, CD54ACT164, CD74ACT164

SCHS240D – NOVEMBER 1998 – REVISED OCTOBER 2024

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