SN74BCT657 OCTAL TRANSCEIVER WITH PARITY GENERATOR/CHECKER AND 3-STATE OUTPUTS

SCBS079B - NOVEMBER 1991 - REVISED APRIL 1994

features

State-of-the-Art BiCMOS Design Significantly Reduces I_CCZ
ESD Protection Exceeds 2000 V Per MIL-STD-883C, Method 3015; Exceeds 200 V Using Machine Model (C = 200 pF, R = 0)
3-State B Outputs Sink 48 mA or 64 mA and Source 12 mA or 15 mA
Package Options Include Plastic Small-Outline (DW) Packages and Standard Plastic 300-mil DIPs (NT)

description

The SN74BCT657 contains eight noninverting transceivers with3-state outputs and an 8-bit parity generator/checker. It is intendedfor bus-oriented applications.

The transmit/receive (T/R\) input determines the direction of thedata flow through the bidirectional transceivers. When T/R\ is high,data is transmitted from the A port to the B port. When T/R\ is low,data is received at the A port from the B port.

When the output-enable ()input is high, both the A and B ports are placed in a high-impedancestate (disabled). The ODD/input allows the user to select between odd or even parity systems.

When transmitting from A port to B port (T/R\ high), PARITY is anoutput from the generator/checker. When receiving from B port to Aport (T/R\ low), PARITY is an input.

When transmitting (T/R\ high), the parity-select (ODD/) input is made high or low asappropriate. The A port is then polled to determine the number ofhigh bits. The PARITY output goes to the logic state determined bythe parity-select (ODD/)input and the number of high bits on A port. When ODD/ is low (for even parity) and thenumber of high bits on A port is odd, the PARITY will be high,transmitting even parity. If the number of high bits on A port iseven, the PARITY will be low, keeping even parity.

When in the receive mode (T/R\ low), the B port is polled todetermine the number of high bits. If ODD/E is low (for even parity) and thenumber of highs on B port is as follows:

Odd and the PARITY input is high, then will be high signifying no error.
Even and the PARITY input is high, then will be low indicating an error.

The SN74BCT657 is characterized for operation from 0°C to70°C.

Title: OCTAL TRANSCEIVER WITH PARITY GENERATOR/CHECKER AND 3-STATE OUTPUTS
Product Family: PARITY TRANSCEIVERS
Device Functionality: BUS TRANSCEIVERS

View the complete PDF datasheet: scbs079b.pdf (106 K Bytes) (Requires Acrobat Reader 3.x)

View more information about generic part numbers:SN74BCT657

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