SN54AS856, SN74AS856

8-BIT UNIVERSAL TRANSCEIVER PORT CONTROLLERS

SDAS032A − DECEMBER 1983 − REVISED MARCH 1985

POST OFFICE BOX 655303

Copyright

1

Outline Packages, Both Plastic and

Ceramic Chip Carriers, and Standard

Plastic and Ceramic 300-mil DIPs

Directly

Functions:

− B to A

− Register to A and/or B

− Off-Line Shifts (A and B Ports in

High-Impedance State)

− Shifted to A and/or B

Analysis Circuitry

− Parallel Storage of Either A or B input

Data

− Serial Transmission of Data from Either

A or B Port

− Readback Mode B to A

Reliability

description

The ’AS856 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

control lines OEA, OEB, and MODE. These

functions include: transferring data from port A to

port B or vice versa (i.e., the transceiver function),

serial shifting data to either or both ports, and

performing off-line shifts (with A and B ports active

as transceivers in a high-impedance state).

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 ’AS856 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 SN54AS856 is characterized for operation over the full military temperature range of −55

°C to 125°C. The

SN74AS856 is characterized for operation from 0

°C to 70°C.

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8

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10

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12

24

23

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20

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13

OEB

OEA

MODE

A1

A2

A3

A4

A5

A6

A7

A8

GND

CLK

SERIN

B1

B2

B3

B4

B5

B6

B7

B8

Q8

SN54AS856 . . . JT PACKAGE

SN74AS856 . . . DW OR NT PACKAGE

(TOP VIEW)

32 1

13 14

5

6

7

8

9

10

11

B1

B2

B3

NC

B4

B5

B6

A1

A2

A3

NC

A4

A5

A6

4

15 16 17 18

SN54AS856 . . . FK PACKAGE

SN74AS856 . . . FN PACKAGE

(TOP VIEW)

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24

23

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21

20

19

12

NC − No internal connection

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.