DS1776QML Datasheet, PDF (11/16 Pages) Texas Instruments – Pi-Bus Transceiver

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DS1776QML
SNOSC82B – AUGUST 2012 – REVISED JUNE 2015
An
Bn ⁽²⁾
H
X
L
X
X
X
—
—
—
H
—
L
—
—
H
X
L
X
X
X
—
H
—
L
—
H
—
L
H
X
L
X
X
X
—
H
—
L
—
H
—
L
Inputs
LE OEA
L
L
L
L
H
L
L
H
H
H
H
H
H
H
L
L
L
L
H
L
L
H
L
H
H
H
H
H
L
L
L
L
H
L
L
H
L
H
H
H
H
H
OEB 0
L
L
L
L
L
L
L
H
H
H
H
H
H
H
X
X
X
X
X
X
X
Table 3. Function Table⁽¹⁾
OEB 1
L
L
L
L
L
L
L
X
X
X
X
X
X
X
H
H
H
H
H
H
H
Latch
State
H
L
Qn
See ⁽³⁾
H ⁽⁴⁾
H ⁽⁴⁾
Qn
H
L
Qn
H
L
Qn
Qn
H
L
Qn
H
L
Qn
Qn
Outputs
An
Bn
Z
H
Z
L
Z
See ⁽²⁾
H
L
Qn
See ⁽²⁾
off ⁽⁴⁾
off ⁽⁴⁾
Qn
Qn
Z
off
Z
off
Z
off
H
off
L
off
H
off
L
off
Z
off
Z
off
Z
off
H
off
L
off
H
off
L
off
Mode
A TRI-STATE, Data from A to B
A TRI-STATE, Latched Data to B
Feedback: A to B, B to A
Preconditioned Latch Enabling
Data Transfer from B to A
Latch State to A and B
B off and A TRI-STATE
B off, Data from B to A
B off and A TRI-STATE
B off, Data from B to A
(1) 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
(2) Condition will cause a feedback loop path; A to B and B to A.
(3) Precaution should be taken to ensure that the B inputs do not float. If they do, they are equal to a Low state.
(4) 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.
6.1 Controller Power Sequencing Operation
The DS1776 has a design feature which controls the output transitions during power up (or down). There are two
possible conditions that occur.
1. When LE = Low and OEBn = 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 allow only one transition during power up (or
down).
2. If LE = High or OEBn = High, then the B outputs still remain disabled during power up (or down).
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