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2

Connection Diagram

Truth Tables

H

= HIGH Voltage Level

L

= LOW Voltage Level

X

= Immaterial (HIGH or LOW, inputs may not float)

Z

= High Impedance

 = LOW-to-HIGH transition

Functional Description

The VCX16821 contains twenty D-type flip-flops with

3-STATE standard outputs. The device is byte controlled

with each byte functioning identically, but independent of

each other. Control pins can be shorted together to obtain

full 20-bit operation. The following description applies to

each byte. The twenty flip-flops will store the state of their

individual D-type inputs that meet the setup and hold time

requirements on the LOW-to-HIGH Clock (CLK) transition.

The 3-STATE standard outputs are controlled by the Out-

outputs are in the high impedance mode but this does not

interfere with entering new data into the flip-flops.

Logic Diagrams

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

XH

X

Z



LL

L



LH

H

L or H

L

X

Inputs

Outputs

XH

X

Z



LL

L



LH

H

L or H

L

X