Periodic calibration for communication channels by drift tracking
A method and system that provides for execution of a first calibration sequence, such as upon initialization of a system, to establish an operation value, which utilizes an algorithm intended to be exhaustive, and executing a second calibration sequence from time to time, to measure drift in the parameter, and to update the operation value in response to the measured drift. The second calibration sequence utilizes less resources of the communication channel than does the first calibration sequence. In one embodiment, the first calibration sequence for measurement and convergence on the operation value utilizes long calibration patterns, such as codes that are greater than 30 bytes, or pseudorandom bit sequences having lengths of 2 N −1 bits, where N is equal to or greater than 7, while the second calibration sequence utilizes short calibration patterns, such as fixed codes less than 16 bytes, and for example as short as 2 bytes long.
1. A method of calibrating a component having a transmitter circuit that is to transmit data to another component, the method comprising:
performing a first calibration operation of the component during an initialization sequence, the first calibration operation to set a value for a parameter pertaining to a driver strength and a termination resistance of the transmitter circuit; and
from time-to-time during normal operation,
performing a second calibration operation to obtain an adjustment to the parameter, such that an update is applied to the value to account for a drift condition.
2. The method of claim 1 , wherein the second calibration operation is to be performed in response to a timer.
3. The method of claim 1 , wherein the second calibration operation is to be performed in response to a detected change in the drift condition.
4. The method of claim 1 , wherein the second calibration operation is to be performed in response to a change in temperature.
5. The method of claim 1 , further comprising transmitting, with the transmitter circuit, a pattern during a calibration operation in which a value for a transmit or receive parameter is to be calibrated.
6. The method of claim 1 , wherein the second calibration operation is performed in association with a change from a first mode of operation to a second mode of operation, and wherein the second mode of operation is a higher speed mode of operation than the first mode of operation.
7. The method of claim 1 , wherein said performing of the first calibration operation is performed to establish each of a first value pertaining to the driver strength and a second value pertaining to the termination resistance, and wherein the method further comprises, from time-to-time, performing a third calibration operation to obtain an adjustment for each of the first value and the second value.
8. A component comprising:
means for performing a first calibration operation of the component during an initialization sequence, the first calibration operation to set a value for a parameter pertaining to a driver strength and a termination resistance of the transmitter circuit; and
means for, from time-to-time during normal operation,
performing a second calibration operation to obtain an adjustment to the parameter, such that an update is applied to the value to account for a drift condition.
9. A component comprising:
a transmitter circuit to transmit data, the transmitter circuit to operate according to a parameter pertaining to a driver strength and a termination resistance; and
a circuit to perform a first calibration operation during an initialization sequence, the first calibration operation to set a value for the parameter, wherein during normal operation, the circuit is to from time-to-time perform a second calibration operation, to obtain an adjustment for the parameter, such that an update is applied to the value to account for a drift condition.
10. The component of claim 9 , wherein circuit is to perform the second calibration operation in response to a timer.
11. The component of claim 9 , wherein the circuit is to perform the second calibration operation in response to a detected change in the drift condition.
12. The component of claim 9 , wherein the circuit is to perform the second calibration operation in response to a change in temperature.
13. The component of claim 9 , further comprising pattern circuitry coupled to the transmitter circuit, transmitter circuit to output a pattern during a calibration operation for which a value for a transmit parameter is to be calibrated.
14. The component of claim 13 , wherein the pattern circuitry is to provide, to the transmitter, a first pattern, having a first length, to the transmitter circuit during the initialization sequence and is to provide a second pattern, having a second length, to the transmitter circuit during a calibration operation performed during normal operation, wherein the first length is longer than the second length.
15. The component of claim 14 , wherein the circuit during normal operation is to iteratively use different values for the transmit parameter and resulting pass/fail samples obtained to determine at two boundaries of a data eye and is to obtain said adjustment dependent on the determined two boundaries.
16. The component of claim 9 , wherein the circuit is to perform said second calibration operation in response to the switch between a first mode of operation and a second mode of operation and wherein the second mode of operation is a higher speed mode of operation than the first mode of operation.
17. The component of claim 9 , wherein the parameter value pertaining to the at least one of the driver strength and the termination resistance of the transmitter circuit comprises a first value pertaining to the driver strength of the transmitter circuit, and a second value pertaining to the termination resistance, and wherein the circuit is to perform said first calibration operation and said second calibration operation with respect to each of the first value and the second value.
18. The component of claim 9 , further comprising a receiver circuit coupled to the transmitter circuit, wherein the transmitter circuit and receiver circuit are used to respectively transmit and receive data via an external link, and wherein the termination resistance is used to terminate the external link.
19. The component of claim 18 , wherein the receiver circuit is to receive a first pattern during the initialization sequence, the first pattern to be used to calibrate a receive parameter of the receiver, the first pattern having a first length, and the receiver circuit is to receive a second pattern, having a second length, during a calibration operation performed during normal operation, wherein the first length is longer than the second length.
20. The component of claim 9 , wherein the second calibration operation is initiated in response to a command.