74ACTQ843CW Просмотр технического описания (PDF) - Fairchild Semiconductor

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74ACTQ843CW

Quiet Series™ 9-Bit Transparent Latch with 3-STATE Outputs

Fairchild Semiconductor 

Functional Description

The ACTQ843 consists of nine D-type latches with 3-

STATE outputs. The flip-flops appear transparent to the

data when Latch Enable (LE) is HIGH. This allows asyn-

chronous operation, as the output transition follows the

data in transition. On the LE HIGH-to-LOW transition, the

data that meets the setup times is latched. Data appears

on the bus when the Output Enable (OE) is LOW. When

OE is HIGH, the bus output is in the high impedance state.

Function Table

In addition to the LE and OE pins, the ACTQ843 has a

Clear (CLR) pin and a Preset (PRE) pin. These pins are

ideal for parity bus interfacing in high performance sys-

tems. When CLR is LOW, the outputs are LOW if OE is

LOW. When CLR is HIGH, data can be entered into the

latch. When PRE is LOW, the outputs are HIGH if OE is

LOW. Preset overrides CLR.

H = HIGH Voltage Level

L = LOW Voltage Level

X = Immaterial

Z = High Impedance

NC = No Change

Inputs

Internal Outputs

Function

CLR PRE OE LE D

Q

O

HHHH L

L

Z

High Z

HHHHH

H

Z

High Z

HHHL X

NC

Z

Latched

HH L H L

L

L

Transparent

HH L HH

H

H

Transparent

HHL L X

NC

NC

Latched

HL LXX

H

H

Preset

LHLXX

L

L

Clear

L L LXX

H

H

Preset

LHHL X

L

Z

Clear/High Z

HLHLX

H

Z

Preset/High Z

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