Gray Code Timestamps for Debug Trace Buffer Integrity
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Solution Overview
Problem
Conventional debug tracing techniques face challenges in efficiently encoding control flow of software running on integrated circuits, leading to potential timestamp errors and inefficient use of trace buffer space.
Innovation Solution
The implementation of Gray coded timestamps and a debug trace circuitry that generates messages responsive to interrupts, watchpoints, and external triggers, storing them in a trace buffer for retrieval by a host device, which includes a Gray code counter to prevent timestamp errors and optimize buffer usage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional debug tracing techniques are used, then the trace buffer can store trace messages, but timestamp errors occur and buffer space is wasted
Solution Approach 1:
The patent changes the timestamp encoding parameter from conventional binary to Gray code representation. This parameter change eliminates timestamp errors by ensuring that only one bit changes between consecutive timestamps, preventing transient errors during counter transitions while maintaining the same buffer space requirements.
Solution Approach 2:
The patent uses a Gray code counter to generate timestamps by copying the counter state through Gray code encoding. This copying mechanism ensures that timestamp transitions are stable and error-free, allowing the trace buffer to utilize space more efficiently by eliminating wasted entries caused by timestamp errors.
2Productivity
If more instructions are traced within a given buffer size, then tracing efficiency improves, but the complexity of managing trace data increases
Solution Approach 1:
By changing the timestamp encoding to Gray code, the patent increases the number of instructions that can be traced within a given buffer size. The Gray code representation eliminates timestamp wraparound errors, allowing the trace buffer to store more valid trace messages without wasting space on erroneous entries, thus improving productivity without significantly increasing management complexity.
Solution Approach 2:
The patent extracts and separates the timestamp generation function into a dedicated Gray code counter module. This extraction simplifies the overall trace data management by isolating the timestamp generation logic, making it easier to implement and maintain while enabling more efficient buffer utilization.
Data Source
AI summary
Systems and methods are disclosed for debug event tracing. For example, an integrated circuit (e.g., a processor) for executing instructions includes a processor core; a data store configured to store a code indicating a cause of an interrupt; a trace buffer configured to store a sequence of debug trace messages; and a debug trace circuitry that is configured to: responsive to a first interrupt to the processor core, generate a first debug trace message including a timestamp and a code from the data store that indicates a cause of the first interrupt; and store the first debug trace message in the trace buffer. In some implementations, the timestamp is generated using a Gray code counter of the integrated circuit.