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Functional Description

The 74F398 and 74F399 are high-speed quad 2-port regis-

ters. They select four bits of data from either of two sources

(Ports) under control of a common Select input (S). The

selected data is transferred to a 4-bit output register syn-

chronous with the LOW-to-HIGH transition of the Clock

input (CP). The 4-bit D-type output register is fully edge-

must be stable only a setup time prior to and hold time after

the LOW-to-HIGH transition of the Clock input for predict-

able operation. The 74F398 has both Q and Q outputs.

Function Table

H

= HIGH Voltage Level

L

= LOW Voltage Level

h

= HIGH Voltage Level one setup time prior to the LOW-to-HIGH

clock transition

I

= LOW Voltage Level one setup time prior to the LOW-to-HIGH

clock transition

X

= Immaterial

Note 1: 74F398 only

Logic Diagram

*F398 Only

Please note that this diagram is provided only for the understanding of logic operations and should not be used to estimate propagation delays.

Inputs

Outputs

QQ

(Note 1)

II

X

L

H

Ih

X

H

L

hX

I

L

H

hX

h

H

L