SN74ALS990_16 Datasheet, PDF (1/14 Pages) Texas Instruments – 8-BIT D-TYPE TRANSPARENT READ-BACK LATCH

SN74ALS990
8-BIT D-TYPE TRANSPARENT READ-BACK LATCH
SDAS027B – APRIL 1984 – REVISED JANUARY 1995
• 3-State I/O-Type Read-Back Inputs
• Bus-Structured Pinout
• True Logic Outputs
• Package Options Include Plastic
Small-Outline (DW) Packages and Standard
Plastic (N) 300-mil DIPs
description
This 8-bit latch is designed specifically for storing
the contents of the input data bus and providing
the capability of reading back the stored data onto
the input data bus.
DW OR N PACKAGE
(TOP VIEW)
OERB 1
1D 2
2D 3
3D 4
4D 5
5D 6
6D 7
7D 8
8D 9
GND 10
20 V_CC
19 1Q
18 2Q
17 3Q
16 4Q
15 5Q
14 6Q
13 7Q
12 8Q
11 LE
The eight latches are transparent D-type latches.
While the latch-enable (LE) input is high, the
Q outputs follow the data (D) inputs.
Read back is provided through the output-enable (OERB) input. When OERB is taken low, the data present at
the output of the data latches is allowed to pass back onto the input data bus. When OERB is taken high, the
output of the data latches is isolated from the D inputs. OERB does not affect the internal operation of the latches;
however, precautions should be taken not to create a bus conflict.
The SN74ALS990 is characterized for operation from 0°C to 70°C.
logic symbol^†
1
OERB
EN2
11
LE
C1
2
1D
1D
2
3
2D
4
3D
5
4D
6
5D
7
6D
8
7D
9
8D
19
1Q
18
2Q
17
3Q
16
4Q
15
5Q
14
6Q
13
7Q
12
8Q
† _{This symbol is in accordance with ANSI/IEEE Std 91-1984 and IEC Publication 617-12.}
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.
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Copyright © 1995, Texas Instruments Incorporated
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