Serial-to-Parallel Loopback Calibration for Memory Controller Timing
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Solution Overview
Problem
Current memory interfaces face challenges in achieving faster memory access due to the difficulty in calibrating high-speed serial links, which require pretraining and are pin-intensive, whereas parallel buses are expensive and inefficient in terms of pin usage.
Innovation Solution
The implementation of a serial-to-parallel loopback configuration for calibrating serial links, allowing for the calibration of high-speed serial links without pretraining, using a parallel interface for receiving serialized data and adjusting timing and framing to ensure accurate data transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a complete serial-to-serial loopback is used for calibration, then the serial link can be calibrated, but the loopback link must be calibrated a priori which increases device complexity and requires pretraining
Solution Approach 1:
The patent introduces a parallel interface as an intermediary component between the serial transmitter and receiver. The parallel interface receives serialized data from the serial transmitter, loops it back through parallel paths, and sends it to the serial receiver. This intermediary parallel interface eliminates the need for the serial loopback link to be calibrated a priori, as the parallel interface handles the data at lower speeds where calibration is not required.
2Device complexity
If a serial bus is used to reduce pin usage, then pin efficiency is improved, but training and calibration become difficult and require pretraining
Solution Approach 1:
The patent segments the calibration process into two distinct phases: a training phase where the serial link is calibrated using the parallel interface as a reference, and an operational phase where normal serial communication occurs. The parallel interface is used only during training to provide known good data for calibration, then is discarded from the operational path. This segmentation allows the serial link to be calibrated without requiring the loopback link to be pre-trained.
Solution Approach 2:
The patent performs preliminary calibration of the serial link using the parallel interface before normal operation begins. During the training phase, the parallel interface provides reference data that allows the serial receiver to learn the correct timing and framing. Once calibration is complete, the system transitions to operational mode where the calibrated serial link handles all communication. This preliminary action using the parallel interface eliminates the need for ongoing pretraining during operation.
Data Source
AI summary
A system and method for calibration of serial links using serial-to-parallel loopback. Embodiments of the present invention are operable for calibrating serial links using parallel links thereby reducing the number of links that need calibration. The method includes sending serialized data over a serial interface and receiving parallel data via a parallel interface. The serialized data is looped back via the parallel interface. The method further includes comparing the parallel data and the serialized data for a match thereof and calibrating the serial interface by adjusting the sending of the serialized data until the comparing detects the match. The adjusting of the sending is operable to calibrate the sending of the serialized data over the serial interface.