Calibration of single-ended high-speed interfaces
View Patent ↗A method for calibrating signal swing and a trip reference voltage. The signal swing of a system can be calibrated in a symmetric or asymmetric technique through adjustment of a drive parameter such as a supply voltage for a transmitter or a drive termination. The trip reference voltage of the system can also be calibrated in a symmetric or asymmetric technique through sampling of a data pattern to determine an ideal level of the trip reference voltage.
1. A method of calibrating a trip reference voltage, the method comprising:
receiving, at a receiving device, a data pattern from a transmitting device via a connection;
comparing, at the receiving device, the data pattern with the trip reference voltage to generate samples of the data pattern;
monitoring, at the receiving device, the samples for data transitions in the data pattern;
determining at the receiving device, a difference between a first time corresponding to a first data transition of the data transitions and a second time corresponding to a second data transition of the data transitions; and
adjusting, at the receiving device, the trip reference voltage based on the difference.
2. The method of claim 1 , wherein the trip reference voltage is adjusted until a duration of time between the data transitions is maximized.
3. The method of claim 1 , further comprising:
setting a sampling point to an average of the first time corresponding to the first data transition of the data transitions and the second time corresponding to the second data transition of the data transitions.
4. The method of claim 1 , wherein the connection is a single-ended connection.
5. A receiving device comprising:
a receiver interface to receive a data pattern from a transmitting device via a connection;
wherein the receiving device compares the data pattern with a trip reference voltage to generate samples of the data pattern, monitors the samples for data transitions in the data pattern, determines a difference between a first time corresponding to a first data transition of the data transitions and a second time corresponding to a second data transition of the data transitions, and adjusts the trip reference voltage based on the difference.
6. The receiving device of claim 5 , wherein the receiving device adjusts the trip reference voltage until a duration of time between the data transitions is maximized.
7. The receiving device of claim 5 , wherein the receiving device sets a sampling point to an average of the first time corresponding to the first data transition of the data transitions and the second time corresponding to the second data transition of the data transitions.
8. The receiving device of claim 5 , wherein the connection is a single-ended connection.
9. A transmitting device, comprising:
a transmitter interface to transmit a data pattern to a receiving device via a connection,
the receiving device comparing the data pattern to a trip reference voltage to generate a sampled version of the data pattern; and
a receiver interface to receive the sampled version of the data pattern from the receiving device;
wherein the transmitting device compares the data pattern to the sampled version of the data pattern and commands the receiving device to adjust the trip reference voltage based on a result of comparing the data pattern to the sampled version of the data pattern.
10. The transmitting device of claim 9 , wherein the transmitting device commands the receiving device to increase the trip reference voltage responsive to the result of comparing the data pattern to the sampled version of the data pattern indicating a data error.
11. The transmitting device of claim 9 , wherein the transmitting device commands the receiving device to lower the trip reference voltage responsive to the result of comparing the data pattern to the sampled version of the data pattern indicating a data error.
12. The transmitting device of claim 9 , wherein the transmitting device uses the result to identify a first level of the trip reference voltage producing data errors and to identify a second level of the trip reference voltage producing data errors, the transmitting device averaging the first level and the second level of the trip reference voltage to generate a setting for the trip reference voltage.
13. The transmitting device of claim 9 , wherein the connection is a single-ended connection.
14. The method of claim 1 , wherein the trip reference voltage is adjusted to maximize a transition free time.
15. The receiving device of claim 5 , wherein the receiving device adjusts the trip reference voltage to maximize a transition free time.