74ACT11657
OCTAL TRANSCEIVER WITH PARITY GENERATOR/CHECKER
AND 3-STATE OUTPUTS

SCAS232 - AUGUST 1992 - REVISED APRIL 1993

features

• Inputs Are TTL-Voltage Compatible
• Flow-Through Architecture Optimizes PCB Layout
• Center-Pin V_CC and GND Pin Configurations Minimize High-Speed Switching Noise
• EPIC^TM (Enhanced-Performance Implanted CMOS) 1-m Process
• 500-mA Typical Latch-Up Immunity at 125°C
• Package Options Include Plastic Small-Outline Packages and Standard Plastic 300-mil DIPs

  EPIC is a trademark of Texas Instruments Incorporated.

   

description

The 74ACT11657 contains eight noninverting buffers with 3-state outputs and an 8-bit parity generator/checker and is intended for bus-oriented applications.

The transmit/receive (T/R\) input determines the direction of data flow through the bidirectional transceivers. 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 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, respectively, on the ODDinput. 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 input. For example, if ODD 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 output logic level indicates whether or not the data to be received exhibits the correct parity sense. For example, if ODDis high (odd parity selected), PARITY is high, and there are three high bits on the B bus, then is low, indicating a parity error.

The 74ACT11657 is characterized for operation from -40°C to 85°C.