SN74BCT979 9-BIT REGISTERED BTL TRANSCEIVER WITH PARITY GENERATOR/CHECKER

SCBS115A - OCTOBER 1990 - REVISED NOVEMBER 1993

features

• 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)
• Support IEEE BTL Standard 1194.1-1991
• Open-Collector B Port Drives Load Impedances as Low as 10
• BTL Logic Level 1-V Bus Swing Reduces Power Consumption
• Latchable Transceiver With Output Sink of 24 mA at the A Bus and 100 mA at the B Bus
• Option to Generate and Check Parity or Feed-Through Data/Parity in Directions A to B or B to A
• Independent Latch Enables for A-to-B and B-to-A Directions
• Select Pin for ODD Parity
• and Output Pins for Parity Checking
• Ability to Simultaneously Generate and Check Parity
• Packaged in 300-mil Plastic Shrink Small-Outline (DL) Package

description

The SN74BCT979 is a 9-bit to 9-bit parity transceiver withtransparent latches. The device can operate as a feed-throughtransceiver, or it can generate/check parity from the 8-bit data busin either direction. It has a guaranteed current-sinking capabilityof 24 mA at the A bus and 100 mA at the open-collector B bus.

The SN74BCT979 features independent latch-enable (LEAB, LEBA)inputs for the A-to-B direction and the B-to-A direction, an ODD input to select odd or evenparity, and separate error-signal (, ) outputs forchecking parity.

When communication between buses occurs, parity is generated andpassed on to either bus as APARO or BPAR. Error detection of theparity generated from AI1-AI8 and B1-B8 can be checked by and, providing LEAB and LEBA are high and the mode select() is low. Ifis high, thecommunication between buses is in a feed-through mode where parity isstill generated and checked as and.

The SN74BCT979 features open-collector driver outputs (B port)with a series Schottky diode to reduce capacitive loading to the bus.By using a 2-V pullup on the bus, the output signal swing will beapproximately 1 V, which reduces the power necessary to drive the busload capacitance. The driver outputs are capable of driving anequivalent dc load of as low as 10 .

The transceiver has a precision threshold set by an internalbandgap reference to give accurate input thresholds overV_CC and temperature variations.

This transceiver is compatible with backplane transceiver logic(BTL) technology at significantly reduced power dissipation perchannel.

The SN74BCT979 is characterized for operation from 0°C to70°C.

View more information about generic part numbers:SN74BCT979

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