SN74ALS845 Datasheet, PDF (1/6 Pages) Texas Instruments – 8-BIT BUS-INTERFACE D-TYPE LATCH WITH 3-STATE OUTPUTS

• 3-State Buffer-Type Outputs Drive Bus
Lines Directly
• Bus-Structured Pinout
• Provides Extra Bus-Driving Latches
Necessary for Wider Address/Data Paths or
Buses With Parity
• Buffered Control Inputs to Reduce
dc Loading Effects
• Power-Up High-Impedance State
• Package Options Include Plastic
Small-Outline (DW) Packages and Standard
Plastic (NT) 300-mil DIPs
description
SN74ALS845
8-BIT BUS-INTERFACE D-TYPE LATCH
WITH 3-STATE OUTPUTS
SDAS233A – DECEMBER 1983 – REVISED JANUARY 1995
DW OR NT PACKAGE
(TOP VIEW)
OE1 1
OE2 2
1D 3
2D 4
3D 5
4D 6
5D 7
6D 8
7D 9
8D 10
CLR 11
GND 12
24 V_CC
23 OE3
22 1Q
21 2Q
20 3Q
19 4Q
18 5Q
17 6Q
16 7Q
15 8Q
14 PRE
13 LE
This 8-bit latch features 3-state outputs designed
specifically for driving highly capacitive or relatively low-impedance loads. This device is particularly suitable
for implementing buffer registers, I/O ports, bidirectional bus drivers, and working registers.
The eight latches are transparent D-type latches. The device has noninverting data (D) inputs and provides true
data at its outputs.
Because the clear (CLR) and preset (PRE) inputs are independent of the clock (CLK) input, taking CLR low
causes the eight Q outputs to go low. Taking PRE low causes the eight Q outputs to go high. When both PRE
and CLR are taken low, the outputs follow the preset condition.
The buffered output-enable (OE1, OE2, and OE3) inputs can be used to place the eight outputs in either a
normal logic state (high or low levels) or a high-impedance state. In the high-impedance state, the outputs
neither load nor drive the bus lines significantly. The high-impedance state and increased drive provide the
capability to drive bus lines without interface or pullup components.
The output enables do not affect the internal operation of the latches. Previously stored data can be retained
or new data can be entered while the outputs are in the high-impedance state.
The -1 version of the SN74ALS845 is identical to the standard version, except that the recommended maximum
I_OL for the -1 version is increased to 48 mA.
The SN74ALS845 is characterized for operation from 0°C to 70°C.
PRE
L
H
H
H
H
X
X
X
CLR
X
L
H
H
H
X
X
X
FUNCTION TABLE
INPUTS
OE1 OE2 OE3 LE
L
L
L
X
L
L
L
X
L
L
L
H
L
L
L
H
L
L
L
L
X
X
H
X
X
H
X
X
H
X
X
X
OUTPUT
D
Q
X
H
X
L
L
L
H
H
L
Q0
X
Z
X
Z
X
Z
PRODUCTION DATA information is current as of publication date.
Products conform to specifications per the terms of Texas Instruments
standard warranty. Production processing does not necessarily include
testing of all parameters.
• POST OFFICE BOX 655303 DALLAS, TEXAS 75265
Copyright © 1995, Texas Instruments Incorporated
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