Communication channel calibration using feedback

A method for calibrating a communication channel coupling first and second components includes transmitting a data signal from the first component to the second component on the communication channel, and sensing a characteristic, such as phase, of the data signal on the second component. Information about the sensed characteristic is fed back to the first component using an auxiliary channel. An adjustable parameter, such as phase, for the transmitter is adjusted on the first component in response to the information. Also, a characteristic of a data signal received from the transmitter on the second component is sensed and used to adjust an adjustable parameter for the receiver on the first component.