Professional ARM Cortex-M Trace Debugging
The SEGGER J-Trace PRO Cortex-M represents a significant advancement in ARM Cortex-M debugging technology. Unlike conventional debug probes that rely on limited internal trace buffers, this professional instrument provides unlimited streaming trace capabilities through high-speed SuperSpeed USB 3.0 and Gigabit Ethernet interfaces.
Streaming Trace Technology
Traditional trace solutions capture instruction data in finite internal buffers, typically 4-32MB, which fills rapidly at high CPU frequencies. The J-Trace PRO Cortex-M eliminates this constraint by continuously streaming trace data to the host computer in real-time. This enables capture periods extending from minutes to months without data loss.
ETM Instruction Tracing
ARM Cortex-M cores with Embedded Trace Macrocell (ETM) capability output detailed instruction execution information through dedicated trace pins. The J-Trace PRO captures this data at up to 150MHz trace clock frequencies, providing complete visibility into program execution flow.
| Trace Type | Information Captured | Use Cases |
|---|---|---|
| Instruction Trace | Every executed instruction with timing | Program flow analysis, performance profiling |
| Data Trace | Memory read/write operations | Data flow debugging, cache analysis |
| Exception Trace | Interrupt and exception handling | RTOS debugging, timing analysis |
Live Analysis Capabilities
The streaming trace architecture enables sophisticated real-time analysis whilst the target executes at full speed. The included Ozone debugger processes trace data as it arrives, providing immediate insights into system behaviour.
Live Code Profiling
Execution profiling operates continuously without target performance impact. The system identifies function execution times, call frequencies, and performance bottlenecks in real-time. Engineers can observe hotspots developing during extended test runs and optimise accordingly.
Live Code Coverage
Instruction-level code coverage monitoring tracks which portions of the application execute during testing. This feature proves essential for safety-critical applications requiring verification that all code paths have been exercised according to regulatory standards such as DO-178C or ISO 26262.
Hardware Architecture
The J-Trace PRO Cortex-M features dual high-speed interfaces for maximum flexibility. SuperSpeed USB 3.0 provides up to 5Gbps bandwidth for streaming trace data, whilst the Gigabit Ethernet interface enables remote debugging scenarios.
| Interface | Bandwidth | Use Case | Benefits |
|---|---|---|---|
| USB 3.0 | 5 Gbps | Direct PC connection | Highest bandwidth, simple setup |
| Gigabit Ethernet | 1 Gbps | Remote debugging | Network access, isolation from EMI |
Target Interface Specifications
The probe provides separate connectors for debug and trace signals. The debug connector supports standard JTAG and SWD protocols at up to 50MHz clock frequencies. The dedicated trace connector handles high-speed ETM data capture.
Debug Connector (20-pin 0.1")
- JTAG: TDI, TDO, TCK, TMS, TRST
- SWD: SWDIO, SWDCLK
- Power: VTref, VCPout, Reset
- Control: nSRST, RTCK
Trace Connector (20-pin 0.05")
- Trace Clock: TRACECLK
- Trace Data: TRACEDATA[3:0]
- SWO: Single Wire Output
- Power and Ground
Software Integration
The J-Trace PRO Cortex-M integrates seamlessly with existing development workflows. The probe operates with all major toolchains and IDEs through standard GDB remote protocol support.
Included Software
- Ozone Debugger: Professional graphical debugger with trace analysis
- J-Flash: High-speed flash programming utility
- J-Link GDB Server: GDB remote protocol server
- RTT Client: Real-Time Transfer communication tool
IDE Compatibility
| Development Environment | Integration Method | Trace Support |
|---|---|---|
| IAR Embedded Workbench | Native plugin | Full ETM analysis |
| Keil µVision MDK | Native plugin | Complete trace features |
| Eclipse CDT | GDB remote protocol | Basic trace viewing |
| Visual Studio Code | Cortex-Debug extension | Trace data export |
Performance Specifications
Key Performance Metrics
- Maximum trace clock frequency: 150 MHz
- Flash programming speed: Up to 4.0 MB/s
- Target interface speed: Up to 50 MHz
- SWO speed: Up to 100 MHz
- Maximum CPU frequency: Unlimited
Trace Setup Example
Setting up streaming trace typically requires minimal target modifications. Most development boards expose trace pins on debug connectors.
Advanced Debugging Scenarios
The unlimited trace capture capability enables debugging scenarios impossible with traditional tools. Engineers can capture complete system execution over extended periods, then analyse the data to identify infrequent bugs or performance degradation patterns.
Hard-to-Reproduce Bug Analysis
Intermittent faults that occur after hours or days of operation can be captured and analysed. The trace data provides complete visibility into the sequence of events leading to the fault condition.
Performance Regression Testing
Long-term performance monitoring identifies gradual degradation in system performance. The live profiling features highlight when functions begin consuming excessive CPU time.
Real-Time System Analysis
RTOS-based applications benefit from complete task switching visibility. The trace data reveals scheduling behaviour, interrupt latencies, and resource contention issues.