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Dsack-clamp

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Dsack clamp

Details

Inventors: Hollyer, Robert; Farrar, Douglas;
Assignee: Apple Computer, Inc. (Cupertino, CA)
Primary Examiner: Shaw; Dale M.
Assistant Examiner: Bhatia; Gaurav
Attorney, Agent or Firm: Blakely, Sokoloff, Taylor & Zafman

A circuit for use in a peripheral interface unit of a microprocessor-based system that actively drives a tri-state data strobe acknowledge (DSACK*) signal to a logical low state after a delay following assertion of an address strobe by the microprocessor. The DSACK* signal is then actively driven to a logical high state in response to deassertion of the address strobe. The DSACK* signal is then returned to a high impedance state. A Schmitt trigger feedback circuit guarantees that the resulting digital "high" level in the high impedance state will exceed a defined, minimum voltage level, regardless of the circuit's capacitance load.

DETAILED DESCRIPTION The present invention provides a circuit for use in a peripheral interface unit of a microprocessor-based system that actively drives a tri-state data strobe acknowledge (DSACK*) signal to a logical low state after a delay following assertion of an address strobe by the microprocessor.
The DSACK* signal is then actively driven to a logical high state in response to deassertion of the address strobe.
The DSACK* signal is then returned to a high impedance state.
A Schmitt trigger feedback circuit guarantees that the resulting digital "high" level in the high impedance state will exceed a defined, minimum voltage level, regardless of the circuit's capacitance load.

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