Pulse Synchronizer Circuit With One-Cycle Clock Domain Crossing
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Solution Overview
Problem
Integrated circuit components operating at different frequencies face significant latency issues when signals cross clock domains due to the use of conventional synchronizer circuits, which introduce multiple clock cycles of delay.
Innovation Solution
A synchronizer circuit is implemented using a first stage flip-flop clocked by the source clock domain and a second stage flip-flop clocked by the target clock domain, with the input of the second stage driven by the output of the first stage and the output generated by XOR-ing both flip-flop outputs, allowing for low-latency synchronization across clock domains.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional synchronizer circuits are used to synchronize signals across clock domains, then signal synchronization reliability is improved, but synchronization latency increases to multiple clock cycles
Solution Approach 1:
The synchronizer circuit is segmented into two distinct stages: a first flip-flop stage operating in the source clock domain and a second flip-flop stage operating in the target clock domain. This segmentation allows each stage to be optimized for its specific clock domain, reducing overall latency while maintaining synchronization reliability.
Solution Approach 2:
The patent inverts the conventional approach by having the first flip-flop clocked by the source clock (rather than target clock) and using XOR logic to generate the synchronized output. This inversion enables the circuit to achieve synchronization with only one source clock cycle latency instead of multiple target clock cycles.
2Speed
If synchronizer circuit latency is reduced to one clock cycle, then communication speed between components is improved, but the circuit complexity increases
Solution Approach 1:
The patent extracts and utilizes the clock signals themselves as part of the synchronization mechanism. By using the source clock to drive the first flip-flop and the target clock to drive the second flip-flop, the circuit leverages existing clock infrastructure rather than adding complex control logic, thereby reducing overall circuit complexity despite achieving low latency.
Solution Approach 2:
The patent changes the clocking parameters of the flip-flops - specifically, the first flip-flop is clocked by the source clock while the second is clocked by the target clock. This parameter change enables the circuit to achieve minimal latency (one source clock cycle) while keeping the implementation relatively simple using standard flip-flop and XOR gate components.
3Adaptability or versatility
If clock frequencies are dynamically adjusted, then system adaptability is improved, but synchronization stability may deteriorate
Solution Approach 1:
The synchronizer circuit is designed to be dynamic, with the first flip-flop responding to changes in the source clock frequency and the second flip-flop responding to changes in the target clock frequency. This dynamic design allows the circuit to maintain proper synchronization even when clock frequencies are adjusted dynamically, preserving both adaptability and stability.
Data Source
AI summary
An integrated circuit to synchronize a pulse signal from a first clock domain to a second clock domain includes a first flip-flop and a second flip-flop. The first flip-flop has a first stage input, a first clock input, and a first stage output. The first clock input is driven by a first clock signal of the first clock domain, and the first stage input is driven by a result of XOR-ing the input pulse signal and the first stage output. The second flip-flop has a second stage input, a second clock input, and a second stage output. The second clock input is driven by a second clock signal of the second clock domain, and the second stage input is driven by the first stage output. The synchronized output pulse signal is generated by XOR-ing the second stage output with the first stage output.