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5

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9

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24

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T/R

A1

A2

A3

A4

A5

A6

A7

A8

ODD/EVEN

ERR

OE

B1

B2

B3

B4

GND

GND

B5

B6

B7

B8

PARITY

DW OR NT PACKAGE

(TOP VIEW)

SN64BCT657

OCTAL TRANSCEIVER WITH PARITY GENERATOR/CHECKER

AND 3STATE OUTPUTS

SCBS090A − NOVEMBER 1991 − REVISED JANUARY 1994

Copyright

3−1

POST OFFICE BOX 655303

POST OFFICE BOX 1443

MIL-STD-883C, Method 3015; Exceeds 200 V

Using Machine Model (C = 200 pF, R = 0)

and Power Down

15 mA

Small-Outline (DW) Packages and Standard

Plastic 300-mil DIPs (NT)

description

The SN64BCT657 contains eight noninverting buffers with parity generator/checker circuits and control signals.

The transmit/receive (T/R) input determines the direction of data flow. When T/R is high, data flows from the

A port to the B port (transmit mode); when T/R is low, data flows from the B port to the A port (receive mode).

When the output-enable (OE) input is high, both the A and B ports are in the high-impedance state.

Odd or even parity is selected by a logic high or low level on the ODD/EVEN input. PARITY carries the parity

bit value; it is an output from the parity generator/checker in the transmit mode and an input to the parity

generator/checker in the receive mode.

In the transmit mode, after the A bus is polled to determine the number of high bits, PARITY is set to the logic

level that maintains the parity sense selected by the level at the ODD/EVEN input. For example, if ODD/EVEN

is low (even parity selected) and there are five high bits on the A bus, then PARITY is set to the logic high level

so that an even number of the nine total bits (eight A-bus bits plus parity bit) are high.

In the receive mode, after the B bus is polled to determine the number of high bits, the error (ERR) output logic

level indicates whether or not the data to be received exhibits the correct parity sense. For example, if

ODD/EVEN is high (odd parity selected), PARITY is high, and there are three high bits on the B bus, then ERR

is low, indicating a parity error.

The SN64BCT657 is characterized for operation from − 40

°C to 85°C and 0°C to 70°C.

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.