Semi Receiver Side Write Training for Non-Volatile Memory
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Solution Overview
Problem
In source synchronous systems, the skew between clock and data signals can lead to incorrect data pulse identification, especially at higher frequencies, and existing write training processes are time-consuming and lack precision due to limitations in semiconductor fabrication, particularly on the receiving side.
Innovation Solution
Implementing semi-receiver side write training where the transmitting device has precise delay taps to control the delay between the clock and data signals, allowing for parallel training across multiple receiving devices and alleviating the need for data feedback, thus enhancing delay resolution and training efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If write training is performed at the transmitter side by transferring test data back to the transmitter for comparison, then the training can be completed with available circuitry, but the training process becomes slow due to the need for data feedback
Solution Approach 1:
Instead of having the transmitter perform the comparison (Tx side training), the patent inverts the approach by having the receiver perform the comparison (Rx side training). The receiver compares received test data with expected data and determines passing delay values, eliminating the need to transfer test data back to the transmitter and significantly reducing training time.
Solution Approach 2:
The patent extracts the comparison function from the transmitter and places it at the receiver. By taking out the data feedback requirement and performing comparisons locally at the receiver, the system eliminates the time-consuming data transfer back to the transmitter while maintaining training effectiveness.
2Loss of time
If write training is performed at the receiver side with local comparison circuitry, then the training time is reduced, but the delay resolution is insufficient due to limitations in semiconductor fabrication processes
Solution Approach 1:
The patent introduces delay taps as an intermediary mechanism between the data strobe signal and user data. These delay taps, controlled by the transmitter, provide fine-grained delay adjustment capability that overcomes the fabrication limitations of the receiver's comparison circuitry. The receiver performs fast local comparisons, and the transmitter uses delay taps to achieve precise delay control based on the receiver's feedback.
Solution Approach 2:
The training function is segmented between the receiver (performing fast local comparisons) and the transmitter (controlling delay taps). This segmentation allows the receiver to operate with relaxed precision requirements while the transmitter provides the necessary fine delay control through programmable delay taps.
3Productivity
If the frequency of data and clock signals is increased to improve transmission speed, then productivity improves, but skew between clock and data signals magnifies causing incorrect data identification
Solution Approach 1:
The patent implements dynamic delay adjustment through programmable delay taps at the transmitter. Instead of using fixed delay values, the system dynamically adjusts the delay between data strobe and user data signals based on training results and operating conditions. This dynamic adjustment compensates for skew that increases with frequency, maintaining reliable data identification at higher transmission speeds.
Data Source
AI summary
Technology is disclosed herein for semi receiver side write training in a non-volatile memory system. The transmitting device has delay taps that control the delay between a data strobe signal and data signals sent on the communication bus. The delay taps on the transmitting device are more precise that can typically be fabricated on the receiving device (e.g., NAND memory die). However, the receiving device performs the comparisons between test data and expected data, which alleviates the need to read back the test data. After the different delays have been tested, the receiving device informs the transmitting device of the shortest and longest delays for which data was validly received. The transmitting device then sets the delay taps based on this information. Moreover, the write training can be performed in parallel on many receiving devices, which is very efficient.