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SDAS234 − D2661, DECEMBER 1982 − REVISED AUGUST 1985
SN54AS877 . . . JT PACKAGE
• Package Options Include Plastic Small
Outline Packages, Both Plastic and
Ceramic Chip Carriers, and Standard
Plastic and Ceramic 300-mil DIPs
SN74AS877 . . . DW OR NT PACKAGE
(TOP VIEW)
S0
S1
S2
A1
A2
A3
A4
A5
A6
V
CC
1
24
23
22
21
20
19
18
17
16
15
14
13
• Buffered 3-State Outputs Drive Bus Lines
CLK
SERIN
B1
B2
B3
B4
B5
B6
B7
2
Directly
3
• Cascaded to n-Bits
4
• Eight Selectable Transceiver/Port
5
Functions:
6
A to B or B to A
7
Register to A or Register to B
Shifted to A or Shifted to B
Off-Line Shifts (A and B Ports in
High-Impedance State)
Register Clear
8
9
A7
A8
GND
10
11
12
B8
Q8
• Particularly Suitable for Use in Signature
Analysis Circuitry
SN54AS877 . . . JT PACKAGE
SN74AS877 . . . DW OR NT PACKAGE
• Serial Register Provides:
Parallel Storage of Either A or B Input
Data
(TOP VIEW)
Serial Transmission of Data from Either
A or B Port
4
3
2 1 28 27 26
• Dependable Texas Instruments Quality and
5
6
7
8
9
25 B1
B2
23 B3
NC
22
B4
21
A1
A2
A3
NC
A4
A5
A6
Reliability
24
description
The ’AS877 features two 8-bit I/O ports (A1-A8
and B1-B8), an 8-bit parallel-load, serial-in,
parallel-out shift register, and control logic. With
these features, this device is capable of
performing eight selectable transceiver or port
functions, depending on the state of the three
select lines S0, S1, and S2. These functions
include: transferring data from port A to port B or
vice versa (i.e., the transceiver function),
transferring data from the register to either port,
B5
20
10
B6
19
11
12 13 14 15 16 17 18
NC − No internal connection
serial shifting data to either port, performing off-line shifts (with A and B ports in high-impedance state), and
clearing the register. Synchronous parallel loading of the internal register can be accomplished from either port
on the positive transition of the clock while serially shifting data in via the SERIN input. The ’AS877 is ideally
suited for applications needing signature-analysis circuitry to enhance system verification and/or fault analysis.
All serial data is shifted right. All outputs are buffer-type outputs designed specifically to drive bus lines directly
and all are 3-state except for Q8, which is a totem-pole output.
The SN54AS877 is characterized for operation over the full military temperature range of −55°C to 125°C. The
SN74AS877 is characterized for operation from 0°C to 70°C.
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Copyright 1985, Texas Instruments Incorporated
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