TABLE 2. Function Table

Inputs

Latch

Outputs

Mode

An

Bn (Note 8)

LE

OEA

OEB

0

OEB

1

State

An

Bn

H

X

L

L

L

L

H

Z

H

A TRI-STATE, Data from A to B

LXL

L

L

L

L

Z

L

X

X

H

L

L

L

Qn

Z

Qn

A TRI-STATE, Latched Data to

B

—

—

L

H

L

L

(Note 10)

(Note 8)

(Note 8)

Feedback: A to B, B to A

—

H

H

H

L

L

H (Note 9)

H

off (Note 9)

Preconditioned Latch Enabling

—

L

H

H

L

L

H (Note 9)

L

off (Note 9)

Data Transfer from B to A

—

—

H

H

L

L

Qn

Qn

Qn

Latch State to A and B

H

X

L

L

H

X

H

Z

off

L

X

L

L

H

X

L

Z

off

B off and A TRI-STATE

X

X

H

L

H

X

Qn

Z

off

—

H

L

H

H

X

H

H

off

—

L

L

H

H

X

L

L

off

—

H

H

H

H

X

Qn

H

off

B off, Data from B to A

—

L

H

H

H

X

Qn

L

off

H

X

L

L

X

H

H

Z

off

L

X

L

L

X

H

L

Z

off

B off and A TRI-STATE

X

X

H

L

X

H

Qn

Z

off

—

H

L

H

X

H

H

H

off

—

L

L

H

X

H

L

L

off

B off, Data from B to A

—

H

H

H

X

H

Qn

H

off

—

L

H

H

X

H

Qn

L

off

H = High Voltage Level

L = Low Voltage Level

X = Don’t Care

— = Input not externally driven

Z = High Impedance (off) state

Qn = High or Low voltage level one setup time prior to the Low-to-High LE transition

Note 8: Condition will cause a feedback loop path; A to B and B to A.

Note 9: The latch must be preconditioned such that B inputs may assume a High or Low level while OEB 0 and OEB 1, are Low and LE is high.

Note 10: Precaution should be taken to ensure that the B inputs do not float. If they do, they are equal to a Low state.

Note 11: off = Applies to “B” (OC) outputs only. Indicates that the outputs are turned off.

CONTROLLER POWER SEQUENCING OPERATION

The DS1776 has a design feature which controls the output

transitions during power up (or down). There are two pos-

sible conditions that occur.

1.

When LE = Low and OEB n = Low, the B outputs are

disabled until the LE circuit can take control. This feature

ensures that the B outputs will follow the A inputs and al-

low only one transition during power up (or down).

2.

If LE = High or OEB n = High, then the B outputs still re-

main disabled during power up (or down).

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