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On-Chip Debugging: JTAG & SWD
How GDB physically reaches into a running chip: built-in debug logic accessed via JTAG (4-5 pins) or ARM's 2-pin SWD, through a debug probe, enabling halt/run, memory access, flashing, and trace.
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What's the difference between JTAG and SWD?How does GDB physically reach into the MCU to halt it and read memory?Why does SWD dominate on ARM Cortex-M devices?You connect a probe but can't talk to the target. What do you check?How can you accidentally "lock yourself out" of debugging, and how do you avoid/recover?
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