SN54ABT657A, SN74ABT657A OCTAL TRANSCEIVERS WITH PARITY GENERATORS/CHECKERS AND 3-STATE OUTPUTS

SCBS192E - JANUARY 1991 - REVISED JUNE 1997

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features

State-of-the-Art EPIC-IIB^TM BiCMOS Design Significantly Reduces Power Dissipation
ESD Protection Exceeds 2000 V Per MIL-STD-883, Method 3015; Exceeds 200 V Using Machine Model (C = 200 pF, R = 0)
Latch-Up Performance Exceeds 500 mA Per JEDEC Standard JESD-17
Typical V_OLP (Output Ground Bounce) < 1 V at V_CC = 5 V, T_A = 25°C
High-Impedance State During Power Up and Power Down
Flow-Through Architecture Optimizes PCB Layout
High-Drive Outputs (-32-mA I_OH, 64-mA I_OL)
Package Options Include Plastic Small-Outline (DW) Packages, Ceramic Chip Carriers (FK), and Plastic (NT) and Ceramic (JT) DIPs

EPIC-IIB is a trademark of Texas Instruments Incorporated.

description

The 'ABT657A transceivers have 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 ODD/EVEN\. For example, if ODD/EVEN\ is low (even parity selected) and there are five high bits on the A bus, 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, ERR\ is low, indicating a parity error.

When V_CC is between 0 and 2.1 V, the device is in the high-impedance state during power up or power down. However, to ensure the high-impedance state above 2.1 V, OE\ should be tied to V_CC through a pullup resistor; the minimum value of the resistor is determined by the current-sinking capability of the driver.

The SN54ABT657A is characterized for operation over the full military temperature range of -55°C to 125°C. The SN74ABT657A is characterized for operation from -40°C to 85°C.

Title: OCTAL TRANSCEIVERS WITH PARITY GENERATORS/CHECKERS AND 3-STATE OUTPUTS
Product Family: PARITY TRANSCEIVERS
Device Functionality: OCTAL BUS TRANSCEIVERS
Orderable Devices: SN74ABT657ADBLE, SN74ABT657ADW, SN74ABT657ADWR, SN74ABT657ANT

View the complete PDF datasheet: scbs192e.pdf (150 K Bytes) (Requires Acrobat Reader 3.x)

View more information about generic part numbers:SN74ABT657A

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