Compliance mode detection from limited information
Consistent with embodiments of the present disclosure, a method involves a redriver circuit with compliance test mode features. A redriver circuit is configured to process received compliance patterns for a compliance test mode. A compliance test mode is detected by a redriver circuit having a first input port and a second input port. The redriver detects the presence of a remote receiver termination on both input ports, monitors both input ports to detect received data and enters compliance test mode in response to no received data being detected on the input ports for a set period of time. Compliance patterns are tracked by monitoring for valid signal levels on the second input port. De-emphasis is controlled on at least one input port in response thereto.
1. A method for configuring a redriver circuit to process received compliance patterns for a compliance test mode, the method comprising:
detecting a compliance test mode for a redriver circuit having a first input port and a second input port by
detecting the presence of a remote receiver termination on both the input ports;
monitoring both the input ports to detect received data; and
entering the compliance test mode in response to no received data being detected on the input ports for a set period of time;
tracking compliance patterns by monitoring for valid signal levels on the second input port; and
enabling and disabling de-emphasis on the first input port in response to the tracked compliance patterns.
2. The method of claim 1 , wherein the compliance test mode is compatible with the Universal Serial Bus (USB) 3.0 protocol.
3. The method of claim 2 , further including the step of monitoring for entrance of into a U0 USB 3.0 link state and wherein the step of entering compliance test mode is further in response to not having detected entrance into the U0 link state.
4. The method of claim 1 , further including the steps of monitoring, after entering compliance test mode, both the first input port and the second input port for a valid signal, determining that the first input port carries compliance patterns by detecting a valid signal on the first input port without first detecting a valid signal on the second input port, and wherein the step of enabling and disabling de-emphasis on the first input port is in response to determining that the first input port carries compliance patterns.
5. The method of claim 1 , further including disabling de-emphasis for compliance patterns 4, 6, and 8 and enabling de-emphasis for compliance patterns 1-3, 5, and 7.
6. The method of claim 1 , further including the steps of tracking compliance patterns by monitoring for valid signal levels on the second port and by disabling the de-emphasis on the first port in response to using detected valid signal levels on the second port to track compliance patterns on the first port.
7. The method of claim 1 , further including the step of tracking compliance patterns by using a squelch monitor on the second port to detect one of a standard LFPS ping and a non standard LFPS ping.
8. A method comprising:
detecting a compliance mode for a redriver circuit having a first input port and a second input port by
detecting the presence of a remote receiver termination on both the input ports;
monitoring both input ports to detected received data; and
determining compliance mode in response to no received data being detected on the input ports for a set period of time;
monitoring each input port to detect a valid data signal level;
determining a compliance pattern has been received by detecting a valid signal level on the first input port, and
configuring, in response to detecting a valid signal level on the first input port, the first input port with de-emphasis and the second input port without de-emphasis.
9. The method of claim 8 , further including the steps of tracking compliance patterns by monitoring for valid signal levels on the second input port and by disabling the de-emphasis on the first input port in response to using detected valid signal levels on the second input port to track compliance patterns on the first input port.
10. The method of claim 9 , wherein the de-emphasis is disabled for compliance patterns 4, 6, and 8 and wherein the de-emphasis is enabled for compliance patterns 1-3, 5, and 7.
11. The method of claim 8 , wherein the re-driver circuit is compliant with the Universal Serial Bus (USB) 3.0 protocol.
12. The method of claim 8 , further including the step of tracking compliance patterns by using a squelch monitor on the second input port to detect one of a standard LFPS ping and a non-standard LFPS ping.
13. A circuit comprising:
logic circuitry configured for
detecting a compliance test mode for a redriver circuit having a first input port and a second input port by
detecting the presence of a remote receiver termination on both input ports;
monitoring both input ports to detected received data; and
entering compliance test mode in response to no received data being detected on the input ports for a set period of time;
tracking compliance patterns by monitoring for valid signal levels on the first input port; and
disabling de-emphasis on the first input port in response to the tracked compliance patterns.
14. The circuit of claim 13 , further including control circuitry configured to determine an upstream or downstream direction of the compliance test mode and to provide de-emphasis on either the first or second input port in response to the determination of direction.
15. The circuit of claim 14 , wherein the control circuitry is further configured to detect low frequency period signaling (LFPS) pings on the other of the first and second port in response to the determination of direction, and to provide de-emphasis control for a currently-provided compliance pattern.
16. The circuit of claim 13 , wherein the redriver circuit is configured to disable de-emphasis on a channel determined to carry LFPS ping data.
17. The circuit of claim 14 , wherein the redriver circuit is configured to make the determination of direction of a compliance test mode without using clock and data recovery circuits.
18. The circuit of claim 13 , wherein logic circuitry is further configured to disable de-emphasis for compliance patterns 4, 6, and 8 and to enable de-emphasis for compliance patterns 1-3, 5, and 7.
19. The circuit of claim 13 , wherein the re-driver circuit is compliant with the Universal Serial Bus (USB) 3.0 protocol.
20. The circuit of claim 13 , further including squelch detectors configured to monitor both input ports to detected received data.