SN74F657 Datasheet | Texas Instruments

description The SN74F657 contains eight noninverting buffers with 3-state outputs and an 8-bit parity generator/checker. It is intended for bus-oriented applications. The buffers have a specified current sinking capability of 24 m A at the A port and 64 m A at the B port. DW OR NT PACKAGE (TOP VIEW) T/R 1 A1 2 A2 3 A3 4 A4 5 A5 6 VCC 7 A6 8 A7 9 A8 10 ODD/EVEN 11 ERR 12 24 OE 23 B1 22 B2 21 B3 20 B4 19 GND 18 GND 17 B5 16 B6 15 B7 14 B8 13 PARITY The transmit/receive (T/R) input determines the direction of the data 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 (OE) input is high, both the A and B ports are placed in a high-impedance state (disabled). The ODD/EVEN 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 an output from the generator/checker. When receiving from B port to A port (T/R low), PARITY is an input. When transmitting (T/R high), the parity select (ODD/EVEN) input is made high or low as appropriate. The A port is then polled to determine the number of high bits.The PARITY output goes to the logic state determined by ODD/EVEN and the number of high bits on A port. When ODD/EVEN is low (for even parity) and the number 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 is even, the PARITY will be low, keeping even parity. When in the receive mode (T/R low), the B port is polled to determine the number of high bits. If ODD/EVEN is low (for even parity) and the number of highs on B port is: 1. Odd and the PARITY input is high, then ERR will be high signifying no error. 2. Even and the PARITY input is high, then ERR will be low indicating an error. The SN74F657 is characterized for operation from 0°C to 70°C. PRODUCTION DATA information is current...