Skew Removal Circuit for Data Transmission Systems
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Solution Overview
Problem
Conventional data transmission systems face limitations in increasing data transmission speed due to skew between data and clock signals, which is exacerbated by time jitter and signal interference, and existing skew removal methods either require additional power or have high circuit overhead and long training times.
Innovation Solution
A skew removal circuit using a first and second clock signal with a phase difference corresponding to half of the data bit period, which includes a skew information extracting unit and a timing control unit to reduce skew by sampling data in a training operating mode and controlling the phase of the transmission sampling clock signal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If conventional source synchronous scheme is used to transmit data and clock signal together, then data transmission speed can be maintained, but skew is generated by mismatch between data line and sampling clock line which limits high-speed operation
Solution Approach 1:
The patent implements a feedback mechanism where the receiving side samples data using two clock signals with different phases, detects skew information from the sampling results, and feeds this information back to the transmitting side. The transmitting side then adjusts the phase of the sampling clock signal based on this feedback to eliminate skew, enabling continuous skew removal during normal data transmission without requiring separate training modes.
Solution Approach 2:
The patent introduces an intermediary mechanism using two clock signals (first clock signal and second clock signal) with a phase difference corresponding to half of the data bit period. These clock signals act as intermediaries to sample data at different phases, allowing the system to detect skew conditions and adjust timing without directly modifying the data transmission path.
2Reliability
If clock data recovery (CDR) method is used to remove skew, then skew between data and clock signal can be removed, but additional power consumption and circuit overhead are required
Solution Approach 1:
The patent makes the existing data transmission system multi-functional by enabling it to perform both data transmission and skew detection/removal functions simultaneously. The same data lines and clock signals used for normal transmission are also utilized for skew detection during training mode, eliminating the need for separate dedicated skew removal circuits and reducing overall power consumption and circuit overhead.
Solution Approach 2:
The system performs self-diagnosis and self-correction by using its own transmitted data and clock signals to detect skew conditions. The receiving side samples its own received data with different clock phases and generates skew information feedback, allowing the system to automatically adjust its timing without requiring external intervention or additional complex circuitry.
3Reliability
If training mode is used for skew removal, then skew can be corrected, but training time is long which reduces productivity
Solution Approach 1:
The patent performs preliminary skew calibration by transmitting training data patterns before normal data transmission begins. During this preliminary training phase, the system establishes the optimal phase relationship between clock and data signals. Once calibrated, the system transitions to normal operation where skew removal continues automatically through feedback mechanisms, minimizing the impact of training time on overall productivity.
Solution Approach 2:
The patent implements dynamic skew removal that adapts to changing conditions. During training mode, the system dynamically adjusts clock phase based on sampled skew information. During normal operation, the feedback mechanism continues to dynamically adjust timing in real-time, allowing the system to respond to temperature drift, voltage changes, and other environmental factors without requiring repeated lengthy training sequences.
Data Source
AI summary
A data transmission/reception system can lessen a skew between data and clock signal by substantially reducing a data reception error. The data transmission/reception system using a first clock signal and a second clock signal having a phase difference corresponding to a half of data bit period as compared with the first clock signal includes a skew information extracting unit and a timing control unit. The skew information extracting unit obtains and outputs skew edge information data necessary for a skew removal by sampling data transmitted in a training operating mode as one of the first and second clock signals in a receiving side. The timing control unit receives the skew edge information data through a transmitting side, and compares its phase with a phase of the transmitted data and controls a timing between transmission data and a transmission sampling clock signal applied to a transmission output unit according to the phase comparison result. Time taken in a training operation can be relatively shortened, and circuits of the receiving side can be simplified and power consumption can be relatively reduced.