Safe communication mode for a high speed link

Patent metadata

Field	Value
Publication number	US-10333565-B2
Application number	US-201815993192-A
Country	US
Kind code	B2
Filing date	May 30, 2018
Priority date	Nov 5, 2015
Publication date	Jun 25, 2019
Grant date	Jun 25, 2019

Abstract

A transmitter for a high speed serial communications link, a serial communications link, and a receiver for a high speed serial communications link are disclosed herein. In one embodiment, the transmitter includes: (1) a communications interface connected to a transmission medium having multiple lanes, and (2) a safe mode circuit coupled to the communications interface and configured to send data over the transmission medium in a safe mode, wherein in the safe mode at least one of the lanes is dedicated to transmitting a link detect signal for link detection.

First claim

What is claimed is:

1. A transmitter for a high speed, serial communications link, comprising:
a communications interface connected to a transmission medium having multiple lanes; and
a safe mode circuit coupled to said communications interface and configured to send data over said transmission medium in a safe mode, wherein in said safe mode at least one of said lanes is dedicated to transmitting a link detect signal for link detection,
said safe mode circuit having a safe mode controller configured to establish a minimum set-up time for said safe mode, wherein said minimum set-up time is greater than a total of a maximum noise width, a strobe/data skew and a minimum set-up time of a receiver connected to said transmission medium.

2. The transmitter as recited in claim 1 further comprising transmission circuitry, different than said safe mode circuit, coupled to said communications interface and configured to send data over said transmission medium in a high speed mode.

3. The transmitter as recited in claim 1 wherein said link detect signal is a constant value.

4. The transmitter as recited in claim 1 wherein in said safe mode, at least two of said lanes are dedicated to link detection.

5. The transmitter as recited in claim 1 wherein in said safe mode, another one of said lanes is dedicated to a data strobe and different ones of said lanes are dedicated to transmit said data in said safe mode.

6. The transmitter as recited in claim 1 wherein in said safe mode, two of said lanes are dedicated to link detection, one of said lanes is dedicated to a data strobe, and four of said lanes are dedicated to transmit said data in said safe mode.

7. The transmitter as recited in claim 1 wherein said safe mode controller is further configured to establish a minimum hold time for said safe mode, wherein said minimum hold time for said safe mode is greater than a total of said maximum noise width, said strobe/data skew and a minimum hold time of said receiver.

8. The transmitter as recited in claim 1 wherein said safe mode circuit encodes said data with bit replication to send said data over said transmission medium in said safe mode.

9. The transmitter as recited in claim 1 wherein said safe mode circuit encodes said data as frequencies to send said data over said transmission medium in said safe mode, wherein separate frequencies are used to represent a value of zero and a value of one.

10. The transmitter as recited in claim 1 wherein said safe mode circuit sends said data over said transmission medium in a safe mode independent of training said transmission medium for high speed operation.

11. The transmitter as recited in claim 1 wherein said safe mode circuit includes a safe mode initializer coupled to said communications interface and a safe mode controller coupled to said communications interface, wherein said safe mode initializer is configured to set-up said serial communications link for said safe mode and said safe mode controller is configured to direct transmission of said data in said safe mode after said set-up.

12. The transmitter as recited in claim 11 wherein said safe mode initializer and said safe mode controller employ safe mode data patterns to set-up said serial communications link for said safe mode and to direct transmission of said data in said safe mode after said set-up.

13. The transmitter as recited in claim 1 further comprising a high speed path and a data interface configured to receive data to transmit over said transmission medium, wherein said safe mode circuit and said high speed path are connected between said data interface and said communications interface and provide separate communication paths therebetween.

14. A serial communications link, comprising:
a transmitter having both a safe mode data transmit path and a high speed data transmit path;
a transmission medium having multiple lanes; and
a receiver coupled to said transmitter via said transmission medium and configured to receive data from said transmitter over at least some of said multiple lanes in both a safe mode and a high speed mode, wherein at least one of said lanes is dedicated to link detection and said transmitter transmits a link detect pattern to said receiver over said at least one of said lanes for said safe mode,
wherein a minimum hold time for said safe mode is greater than a total of a maximum noise width, a strobe/data skew and a minimum hold time of said receiver.

15. The serial communications link as recited in claim 14 wherein in said safe mode, said transmitter transmits said data to said receiver without deskewing said multiple lanes.

16. The serial communications link as recited in claim 14 wherein said transmission medium includes multiple lanes and each of said lanes are used to transmit data in a high speed mode and less than all of said lanes are used to transmit data in said safe mode.

17. The serial communications link as recited in claim 14 wherein said serial communications link operates in said safe mode, a training mode and said high speed mode, wherein said safe mode is independent of said training mode and said high speed mode is dependent on said training mode.

18. A receiver for a high speed, serial communications link, comprising:
a receive interface connected to a transmission medium having multiple lanes;
receiving circuitry coupled to said receive interface and configured to receive data from said transmission medium in a high speed mode; and
a safe receive circuit, different than said receiving circuitry, coupled to said receive interface and configured to receive data from said transmission medium in a safe mode, wherein in said safe mode at least one of said lanes is dedicated to a link detect signal for link detection,
wherein a minimum set-up time of said safe mode is greater than a total of a maximum noise width, a strobe/data skew and a minimum set-up time of said receiver, and a minimum hold time of said safe mode is greater than a total of said maximum noise width, said strobe/data skew and a minimum hold time of said receiver.

19. The receiver as recited in claim 18 wherein said safe receive circuit is further configured to determine lane reversal and polarity reversal of at least some of said multiple lanes.

20. The receiver as recited in claim 19 wherein said safe receive circuit is further configured to detect said link detect signal and operate in said safe mode after determining said lane reversal and said polarity reversal.

Assignees

• Nvidia Corp

Inventors

• Ma Dennis
• Denman Marvin
• Tyson Eric
• Glaser Stephen D

Classifications

• H04L25/0276

  Arrangements for coupling common mode signals · CPC title

• G06F21/83

  input devices, e.g. keyboards, mice or controllers thereof · CPC title

• H04L25/0264 Primary

  Arrangements for coupling to transmission lines (duplexing arrangements H04L5/14; line equalisers, line build-out devices H04L25/03878) · CPC title

• H04B1/04 Primary

  Circuits · CPC title

• H04M7/126

  Interworking of session control protocols · CPC title