eMMC Delay Offset Adjustment for Timing Skew
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Solution Overview
Problem
Embedded Multimedia Cards (eMMCs) face challenges in securing an improved data valid window due to timing skew issues when communicating with hosts, particularly at high clock speeds like in the DDR 400 mode, which affects data transmission speed and reliability.
Innovation Solution
The eMMC system employs a method to adjust data signal delays using delay offset values stored in the EXT_CSD register, with a host transmitting a SWITCH command and Get Tuning Block command to determine valid data signals and set optimal delay offsets, and includes delay circuits to adjust clock and data signals based on calculated codes for improved timing alignment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If data signals are transmitted at high clock speeds (DDR 400 mode), then data transmission speed is improved, but timing skew between clock and data signals increases causing data validity issues
Solution Approach 1:
The patent applies preliminary action by performing delay adjustment before data transmission. The host controller sends a SWITCH command with delay offset values to the eMMC, which then adjusts the delay of data signals using delay circuits before actual data transfer occurs. This pre-adjustment ensures proper timing alignment is established in advance, preventing timing skew issues during high-speed operation.
Solution Approach 2:
The patent implements parameter changes by dynamically modifying the delay parameter of data signals. The eMMC receives delay offset values and changes the delay parameter of its data signals accordingly. This allows the system to optimize timing parameters for different operating conditions and clock speeds, maintaining data validity while enabling high-speed transmission.
2Reliability
If delay adjustment is performed to correct timing skew, then data signal validity is improved, but system complexity increases due to additional control commands and delay circuits
Solution Approach 1:
The patent applies universality by making the SWITCH command multi-functional. The existing SWITCH command, traditionally used for mode switching, is extended to also carry delay offset values for timing adjustment. This allows the system to perform both mode switching and delay adjustment using a single command mechanism, reducing the need for separate control structures and minimizing system complexity.
Solution Approach 2:
The eMMC performs self-service by automatically adjusting its own data signal delays based on received offset values. The delay circuits within the eMMC are controlled locally using the provided delay parameters, eliminating the need for external delay adjustment circuitry in the host. This self-adjusting capability simplifies the overall system architecture while maintaining reliable timing alignment.
Data Source
AI summary
An embedded multimedia card (eMMC) is provided. The eMMC includes a clock channel receiving a clock output from a host, data channels receiving data signals from the host, and a command channel receiving a SWITCH command including delay offset values from the host so as to adjust a delay of at least one of the data signals, which are received, in response to the delay offset values.