Clock Regeneration in Daisy-Chained Devices for Data Timing Integrity
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Solution Overview
Problem
In cascaded electronic devices, the common clock signal can suffer from skewing and loss due to buffering, leading to data integrity issues, especially in long daisy-chains with high data rates, and there are challenges in ensuring sufficient hold and setup times for data transfer.
Innovation Solution
A device with a clock input port and output port, featuring a clock circuit that regenerates the clock signal with a period equal to the input signal and independent duty cycle, and a data output alignment circuit that synchronizes data with non-clock-triggering edges to ensure proper timing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a common clock signal is used to ensure synchronous data transfer in cascaded devices, then data integrity is maintained, but the drive requirements and noise susceptibility increase significantly
Solution Approach 1:
The patent divides the single common clock signal into multiple segmented clock signals, with each cascaded device generating its own clock output from the clock input. This segmentation eliminates the need for a single high-power common clock line while maintaining synchronous operation across all devices.
Solution Approach 2:
Each device acts as an intermediary by receiving the clock signal and regenerating it for the next device in the chain. This intermediary approach allows the clock signal to be distributed throughout the daisy-chain without requiring a high-power common clock line, thereby reducing drive requirements while maintaining data integrity.
2Power
If the clock signal is buffered at each device to reduce drive requirements, then power consumption is reduced, but clock signal skewing and loss occur leading to data integrity issues
Solution Approach 1:
The patent changes the parameters of the clock signal by requiring that the clock output signal have a period substantially equal to the clock input signal period and a duty cycle that is independent of the input duty cycle. This parameter transformation ensures that cumulative skewing is prevented while still allowing buffering at each device to reduce drive requirements.
Solution Approach 2:
The patent implements a feedback mechanism where each device monitors its clock input signal characteristics and adjusts its clock output signal to maintain the correct period and duty cycle. This feedback ensures that clock signal integrity is maintained throughout the daisy-chain even with multiple buffering stages.
3Ease of operation
If a long daisy-chain of devices is used to meet application requirements, then device connectivity is simplified, but clock signal noise and reflections increase
Solution Approach 1:
The patent segments the long daisy-chain into multiple shorter clock signal paths, with each device generating its own clock output. This segmentation reduces the length of each clock signal line, thereby minimizing noise and reflections while maintaining the simplified daisy-chain connectivity architecture.
4Productivity
If high data rates are used to meet performance requirements, then productivity is improved, but clock signal skewing and loss increase in long chains
Solution Approach 1:
The patent transforms the clock signal parameters by ensuring that each device outputs a clock signal with a period substantially equal to its input clock period and a duty cycle that is independent of the input duty cycle. This parameter transformation allows high data rates to be maintained while preventing cumulative skewing that would otherwise cause data integrity issues in long cascaded chains.
Data Source
AI summary
Apparatus and methods for processing a clock input signal with a clock regeneration circuit to provide a clock output signal for coupling to a cascaded device. The clock output signal has a period substantially equal to the period of the clock input signal and a duty cycle independent of the duty cycle of the clock input signal. In one embodiment, the clock regeneration circuit includes a one-shot and a buffer. Also described are apparatus and methods for aligning a data output signal of a cascaded device to non-clock-triggering edges of a selected one of the clock input signal and the clock output signal.