USB2 PHY Interface for Closed Chassis Debug Control Signaling
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Solution Overview
Problem
Current methods for debug control interface (DCI) signaling in closed chassis systems, such as tablets, are limited by the inability to open the chassis for testing, and existing solutions like USB3.1 Type-C connectors face issues with single-ended signaling and increased platform bill of materials costs due to the need for multiplexors.
Innovation Solution
The use of Universal Serial Bus 2.0 (USB2) pins for DCI signaling through Type-C and non-Type-C connectors, with flexible lane configuration and self-generated clocks to enable DCI signaling without a controller or power management controller handshake, allowing for reduced power consumption and robust interface signaling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If USB3.1 Type-C connector is used for DCI signaling, then higher operating frequency and flexibility are achieved, but single-ended signaling compatibility and platform cost are worsened due to multiplexor requirements
Solution Approach 1:
The patent extracts the DCI signaling function from the high-speed USB3.1 protocol framework and implements it using the lower-speed USB2.0 protocol instead. This extraction allows the system to use simple differential signaling without requiring complex multiplexors or single-ended signaling compatibility, thereby reducing device complexity while maintaining the ability to perform debug control interface functions through the Type-C connector.
Solution Approach 2:
The patent chooses to use USB2.0 pins instead of USB3.1 pins for DCI signaling. USB2.0 is a more mature, simpler, and more cost-effective protocol compared to USB3.1. By using the older, simpler protocol for the debug interface, the system avoids the need for expensive multiplexors and complex signal conditioning circuits, thereby reducing the platform bill of materials cost.
2Productivity
If USB3.1 super speed lane is used for BSSB signaling, then data transmission capability is improved, but platform bill of materials cost increases due to multiplexor addition
Solution Approach 1:
The patent makes the USB2.0 pins multi-functional by allowing them to serve both standard USB2.0 communication purposes and DCI/BSSB signaling functions. This universality eliminates the need for dedicated separate pins or complex multiplexing hardware, thereby reducing the platform BOM cost while maintaining adequate data transmission capability for debug operations.
Solution Approach 2:
The patent uses the existing USB2.0 physical layer infrastructure to carry DCI signaling, essentially copying the USB2.0 signaling mechanism for debug purposes. This approach leverages the already-present USB2.0 transceivers and pins, avoiding the need to add expensive USB3.1 multiplexor hardware, thereby reducing platform BOM cost while providing sufficient data transmission capability for boundary scan and debug operations.
3Ease of operation
If chassis is opened for device testing, then access to device for testing is improved, but system integrity and security are worsened
Solution Approach 1:
The patent introduces an intermediary debug interface that allows testing without physical access to internal device pins. By using the existing USB Type-C connector and USB2.0 pins as an intermediary channel, the system enables boundary scan and debug operations through software-controlled signaling, eliminating the need to open the chassis while maintaining system integrity and security.
Solution Approach 2:
The patent replaces the mechanical approach of physically opening the chassis and connecting testers to internal pins with an electronic/software-based approach. By using USB2.0 electrical signaling through the closed chassis's existing connector, the system eliminates the mechanical intervention entirely, thereby maintaining system integrity and security while enabling debug operations.
Data Source
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AI summary
A system, method and apparatus for enabling a closed chassis debug control interface are disclosed. In one embodiment, the system comprises a debug mode control (DCI) unit; a Type-C connector; a Universal Serial Bus (USB) physical (phy) interface coupled to the connector; and interface logic coupled to the DCI unit and the USB phy interface to exchange debug control interface (DCI) signaling between the connector and the DCI unit.