Abstract: A system utilizing distributed on-chip termination. The system comprises a bus having a signal line and a first bus agent which is coupled to the bus. The first bus agent has a first termination circuit which is coupled to selectably terminate the signal line to a termination voltage. The system may further comprise an additional bus agent. The additional bus agent has a second termination circuit coupled to selectably terminate the signal line to the termination voltage. The bus in the system has a bus impedance, and the impedance of the termination circuit(s) is typically greater than twice the bus impedance.

Abstract: A method and apparatus for glitch protection for differential strobe input buffers in a source-synchronous environment. The present invention provides a solution to the problem of noise sensitivity of differential strobe input buffers in a source-synchronous environment, which may cause functional problems. The present invention enables the use of fully differential strobe signals to improve electrical performance of the source synchronous data transfers while removing the noise sensitivity problem associated with these signals. This is accomplished by providing a glitch protection circuit that provides protection against input glitches for a first predetermined period of time after each strobe transition. The present invention also provides a detection circuit that detects when both differential strobe signals are in the same logic state, which corresponds to a transition between bus masters (a dead cycle).

Abstract: A method and an apparatus for adjusting the slew rate and impedance of a buffer in an integrated circuitry. In one embodiment, an integrated circuit buffer includes a pre-driver circuit, which includes a slew rate compensation circuit, coupled to a driver circuit, which includes an impedance compensation circuit. The slew rate compensation circuit includes parallel connected p-channel transistors to power and parallel connected n-channel transistors to ground to provide a variable resistance to virtual rails for inverter circuits that are included in the pre-driver circuit. The slew rate compensation circuit is digitally controlled with slew rate control signals. The impedance compensation circuit includes parallel connected p-channel transistors to power and parallel connected n-channel transistors to ground from an output node of the buffer. The parallel connected transistors of the impedance compensation circuit are digitally controlled with impedance control signals.

Abstract: A method and an apparatus for controlling compensated buffer circuits. In one embodiment, a compensation buffer control circuit includes a compensation unit with a compensation signal memory location such as a compensation register. The compensation unit is configured to produce a local compensation control signal to control a compensated buffer circuit. The compensation signal memory location is configured to selectively receive and store and the local compensation control signal generated by the compensation unit. The contents of the compensation signal memory location may be read, which allows for the external reading of the local compensation signal generated by the compensation unit. In addition, an external write of an external compensation control signal may be performed to the compensation signal memory location such that the output of the compensation unit can be overridden.

Abstract: A self-testing buffer circuit. The buffer circuit utilizes an adjustable delay circuit to test whether the buffer can capture a data value during a variable stroke window. The buffer includes an input circuit coupled to receive a data value generated by the self-testing buffer circuit. The buffer circuit also includes a latch which has a latch input coupled to receive the data value from the input circuit. An adjustable delay circuit having a delay adjust input is coupled to provide an adjustably delayed strobe to a clock input of the latch. A comparison circuit may be coupled to compare a latch output value to an expected value. The self-testing buffer circuit may be used in conjunction with serial or parallel test resisters to test the buffer performance for a variety of strobe delays and data values.

Abstract: An opportunistic time-borrowing domino logic includes a domino pipeline having a plurality of logic gates coupled in series and controlled by first, second, third and fourth clock signals. The first domino gate in a half-cycle is clocked by either the first or the second clock signals, wherein the last domino gate in a half-cycle is clocked by either the third or the fourth clock cycles. The second clock signal is an inverse of the first clock signal, and the third and fourth clock signals have local delayed clock phases in which the falling edges of the third and fourth clock signals are delayed relative to the falling edges of the respective first and second clock signals. In a first half-cycle, a first type of domino gate is controlled by the first clock signal, with subsequent domino gates of the same type being controlled by the third clock signal.