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2

Functional Description

The 74F399 is a high-speed quad 2-port registers. 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 synchronous

with the LOW-to-HIGH transition of the Clock input (CP).

The 4-bit D-type output register is fully edge-triggered. The

only a setup time prior to and hold time after the LOW-to-

HIGH transition of the Clock input for predictable operation.

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

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

Q

II

X

L

Ih

X

H

hX

I

L

hX

h

H