Multi-Clock Domain Trace Synchronization via Global Timestamp
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Solution Overview
Problem
As integrated circuits become more complex, tracing and debugging across multiple modules with separate clock domains become increasingly challenging, leading to difficulties in identifying and eliminating functional bugs, as existing tracing solutions are insufficient for capturing accurate trace data due to clock skew and limited capacity to handle multiple data sources.
Innovation Solution
The implementation of a debug module with a global time stamp counter and synchronization latches allows for the synchronization of trace records across multiple clock domains, enabling simultaneous storage of trace data from multiple sources with both coarse and fine time stamps, and providing a central control for tracing and debugging operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If separate clock domains are used for different modules, then system performance and modularity are improved, but trace data correlation and debugging accuracy deteriorate due to clock skew
Solution Approach 1:
A global time stamp counter acts as an intermediary mechanism that receives trace data from multiple clock domains and timestamps each record with a unified time reference. This mediator enables accurate correlation of trace records across different clock domains by providing a common time baseline, resolving the clock skew problem without requiring clock synchronization between domains.
Solution Approach 2:
The trace buffer is segmented into multiple partitions, with each partition dedicated to storing trace records from a specific clock domain. This segmentation allows independent storage of traces from different domains while maintaining organization, and enables the system to handle multiple data sources simultaneously without interference between domains.
2Difficulty of detecting and measuring
If trace data from multiple sources is stored simultaneously, then debugging capability is improved, but device complexity increases due to synchronization requirements
Solution Approach 1:
The global time stamp counter serves as a simple intermediary that adds a time reference to trace records without requiring complex synchronization protocols. Each clock domain simply needs to provide its trace data, and the global counter timestamps each record, enabling simultaneous storage from multiple sources with minimal added complexity.
Solution Approach 2:
By dividing the trace buffer into domain-specific partitions, the system can store traces from multiple clock domains independently without requiring complex coordination. Each partition handles its own domain's traces, simplifying the overall synchronization mechanism while enabling multi-source debugging capability.
3Device complexity
If clock skew is not compensated, then device complexity is reduced, but measurement precision of trace timing deteriorates
Solution Approach 1:
The global time stamp counter acts as a mediator that compensates for clock skew by providing a unified time reference for all trace records. Instead of requiring complex clock synchronization across domains, the system simply timestamps each trace record with the global counter's current value, accurately capturing timing information despite varying clock frequencies and phases in different domains.
Data Source
AI summary
An integrated circuit with multiple clock domain tracing capability includes a debug module including a global time stamp counter for counting pulses of a reference clock signal to provide a global time stamp, a first granularity counter for counting pulses of a first clock signal to provide a first granularity count, a second granularity counter for counting pulses of a second clock signal to provide a second granularity count and a trace cache buffer for selectively storing in a first partition the global time stamp, the first granularity count, and first data synchronous to the first clock signal, and for selectively storing in a second partition the global time stamp, the second granularity count, and second data synchronous to the second clock signal.