System and method to enhance feed-forward equalization in a high-speed serial interface

• US 10,298,420 B1
• Filed: 03/20/2018
• Issued: 05/21/2019
• Est. Priority Date: 03/20/2018
• Status: Active Grant

• Current Assignee: Dell Products LP (Dell Technologies Inc.)
• Original Assignee: Dell Products LP (Dell Technologies Inc.)
• Inventors: Chada, Arun R., Deng, Han, Mutnury, Bhyrav M.
• Primary Examiner(s): Panwalkar, Vineeta S
• Application Number:
  US15/926,525
• Time in Patent Office: 427 Days
• CPC Class Codes: H04L 25/03025 using a two-tap delay line
• CPC Class Codes: H04L 25/03343 Arrangements at the transmitter end
• CPC Class Codes: H04L 25/03878 Line equalisers; line build-out devices
• CPC Class Codes: H04L 7/0058 detection of error based on equalizer tap values

Abstract

A high-speed serial data interface includes a transmitter and a receiver. The transmitter includes a feed-forward equalization (FFE) module. The FFE module has a main tap and at least one secondary tap. In a first mode, a sum of absolute values of a main tap compensation value and a secondary tap compensation value of each one of the at least one secondary tap is equal to one. In a second mode, the main tap compensation value has a unity gain equal to one, and each secondary tap compensation value is greater than or equal to the secondary tap compensation value in the first mode divided by the main tap compensation value in the first mode.

Claims

1. A high-speed serial data system, comprising:

a receiver; and

a transmitter including a feed-forward equalization module having a main tap and at least one secondary tap, wherein in a first mode a sum of absolute values of a main tap compensation value and a secondary tap compensation value of each of the secondary taps is equal to 1, and wherein in a second mode the main tap compensation value has a unity gain equal to 1, and each secondary tap compensation value is greater than or equal to the secondary tap compensation value in the first mode divided by the main tap compensation value in the first mode.

2. The serial data system of claim 1, wherein the at least one secondary tap includes a post-tap that is delayed from the main tap by at least one unit interval.

3. The serial data system of claim 2, wherein the at least one secondary tap further includes a pre-tap that is advanced from the main tap by at least on unit interval.

4. The serial data system of claim 1, wherein in the second mode, each secondary tap compensation value set to be equal to the secondary tap compensation value in the first mode divided by the main tap compensation value in the first mode.

5. The serial data system of claim 4, wherein further in the second mode the transmitter receives an indication from the receiver to change at least one secondary tap compensation value in response to setting each secondary tap compensation value to be equal to the secondary tap compensation value in the first mode divided by the main tap compensation value in the first mode.

6. The serial data system of claim 4, wherein further in the second mode the transmitter sets at least one secondary tap compensation value to greater than the secondary tap compensation value in the first mode divided by the main tap compensation value in the first mode in response to receiving the indication.

7. The serial data system of claim 1, wherein the receiver includes a compensation module that is enabled when the transmitter is in the first mode and that is disabled when the transmitter is in the second mode.

8. A method of providing equalization in a high-speed serial data system, the method comprising:

setting, in a first mode, a main tap compensation value of a main tap of a feed-forward equalizer of a transmitter of the serial data system, and each of a secondary tap compensation value of at least one secondary tap of the feed-forward equalizer, wherein in setting the main tap compensation value and each secondary tap compensation value in the first mode, a sum of absolute values of the main tap compensation value and each secondary tap compensation values is equal to 1;

setting, in a second mode, the main tap compensation value to have a unity gain equal to 1; and

setting, in the second mode, each secondary tap compensation value such that each secondary tap compensation value is greater than or equal to the secondary tap compensation value in the first mode divided by the main tap compensation value in the first mode.

9. The method of claim 8, wherein the at least one secondary tap includes a post-tap that is delayed from the main tap by at least one unit interval.

10. The method of claim 9, wherein the at least one secondary tap further includes a pre-tap that is advanced from the main tap by at least on unit interval.

11. The method of claim 8, wherein further in the second mode and prior to setting each secondary tap compensation value such that each secondary tap compensation value is greater than or equal to the secondary tap compensation value in the first mode divided by the main tap compensation value in the first mode, the method further comprises:

setting each secondary tap compensation value to be equal to the secondary tap compensation value in the first mode divided by the main tap compensation value in the first mode.

12. The method of claim 11, wherein in response to setting each secondary tap compensation value to be equal to the secondary tap compensation value in the first mode divided by the main tap compensation value in the first mode, the method further comprises:

receiving, by the transmitter, an indication from a receiver of the serial data system to change at least one secondary tap compensation value.

13. The method of claim 11, wherein in response to receiving the indication, the method further comprises:

setting at least one secondary tap compensation value to greater than the secondary tap compensation value in the first mode divided by the main tap compensation value in the first mode in response to receiving the indication.

14. The method of claim 8, further comprising:

enabling a compensation module in the receiver when the transmitter is in the first mode; and

disabling the compensation module when the transmitter is in the second mode.

15. A feed-forward equalizer (FFE) for a transmitter of a high-speed serial data system, the FFE comprising:

a main tap; and

at least one secondary tap, wherein in a first mode a sum of absolute values of a main tap compensation value and a secondary tap compensation value of each of the secondary taps is equal to 1, and wherein in a second mode the main tap compensation value has a unity gain equal to 1, and each secondary tap compensation value is greater than or equal to the secondary tap compensation value in the first mode divided by the main tap compensation value in the first mode.

16. The FFE of claim 15, wherein the at least one secondary tap includes a post-tap that is delayed from the main tap by at least one unit interval.

17. The FFE of claim 16, wherein the at least one secondary tap further includes a pre-tap that is advanced from the main tap by at least on unit interval.

18. The FFE of claim 15, wherein in the second mode, each secondary tap compensation value set to be equal to the secondary tap compensation value in the first mode divided by the main tap compensation value in the first mode.

19. The FFE of claim 18, wherein further in the second mode the transmitter receives an indication from the receiver to change at least one secondary tap compensation value in response to setting each secondary tap compensation value to be equal to the secondary tap compensation value in the first mode divided by the main tap compensation value in the first mode.

20. The FFE of claim 18, wherein further in the second mode the transmitter sets at least one secondary tap compensation value to greater than the secondary tap compensation value in the first mode divided by the main tap compensation value in the first mode in response to receiving the indication.