Datasheet


   
      
SCES566F − MAY 2004 − REVISED APRIL 2005
2
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
description/ordering information (continued)
The SN74AVC20T245 is designed for asynchronous communication between data buses. The device transmits
data from the A bus to the B bus or from the B bus to the A bus, depending on the logic level at the
direction-control (DIR) input. The output-enable (OE
) input is used to disable the outputs so that the buses are
isolated.
The SN74AVC20T245 is designed so that the control (1DIR, 2DIR, 1OE
, and 2OE) inputs are supplied by V
CCA
.
This device is fully specified for partial-power-down applications using I
off
. The I
off
circuitry disables the outputs,
preventing damaging current backflow through the device when it is powered down.
The V
CC
isolation feature ensures that if either V
CC
input is at GND, both ports are in the high-impedance state.
To ensure the high-impedance state during power up or power down, OE
should be tied to V
CC
through a pullup
resistor; the minimum value of the resistor is determined by the current-sinking capability of the driver.
terminal assignments
123456
A 1B1 1B2 1DIR 1OE 1A2 1A1
B 1B3 1B4 GND GND 1A4 1A3
C 1B5 1B6 V
CCB
V
CCA
1A6 1A5
D 1B7 1B8 GND GND 1A8 1A7
E 1B9 1B10 1A10 1A9
F 2B1 2B2 2A2 2A1
G 2B3 2B4 GND GND 2A4 2A3
H 2B5 2B6 V
CCB
V
CCA
2A6 2A5
J 2B7 2B8 GND GND 2A8 2A7
K 2B9 2B10 2DIR 2OE 2A10 2A9
FUNCTION TABLE
(each 10-bit section)
INPUTS
OPERATION
OE
DIR
OPERATION
L L B data to A bus
L H A data to B bus
H X Isolation
GQL OR ZQL PACKAGE
(TOP VIEW)
J
H
G
F
E
D
C
B
A
213465
K