US Patent 7356555 In-protocol impedance compensation control

One embodiment of a technique for performing impedance compensation update operations without causing potential data corruption problems includes taking advantage of protocol idle periods, where synchronization primitives, filler data, and alignment primitives are being transmitted. For example, a serial interconnect controller may take control of the interconnect by initiating a dummy transaction. The controller can then perform an impedance compensation update operation while it is assured that no data transfers are occurring. After an appropriate settling time and after a transmission of an alignment primitive, the controller can complete the dummy transaction by issuing a no-op. This process may be re-performed periodically.