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Method and apparatus for dual mode output buffer impedance compensation

  • US 6,166,563 A
  • Filed: 04/26/1999
  • Issued: 12/26/2000
  • Est. Priority Date: 04/26/1999
  • Status: Active Grant
First Claim
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1. A method of programming an output buffer having a first output driver for producing a first signaling level with a first programmable strength and a second output driver for producing a second signaling level with a second programmable strength, the method comprising:

  • coupling a test resistor between a source of the second signaling level and a mode terminal;

    sensing a first level at the mode terminal;

    uncoupling the test resistor from the mode terminal;

    if the first level is between the second signaling level and a reference level, then programming the output buffer with reference to an unterminated transmission line coupled to the mode terminal;

    otherwise,programming the output buffer with reference to an external resistor coupled between a source of the first signaling level and the mode terminal.

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