18 lines
819 B
Markdown
18 lines
819 B
Markdown
# FC07 — real external IRQ and semaphore handoff
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This card drives Hazard3 external IRQ input 5 through testbench MMIO. The
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external vector enters the official FreeRTOS full-context trap path, switches to
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`xISRStack`, calls an application ISR and returns through the context selected
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by `portYIELD_FROM_ISR()`.
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The ISR clears the hardware source before `xSemaphoreGiveFromISR()`. Because a
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priority-3 waiter is blocked while a priority-2 stimulus is interrupted,
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`xHigherPriorityTaskWoken` becomes `pdTRUE`. Evidence E07 proves that the waiter
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runs before E08, where the interrupted stimulus continues after its MMIO store.
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```sh
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make check
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python3 /home/user/dev/workspace/stem/tools/card-layouts/tools/build_freertos_c_card.py .
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python3 /home/user/dev/workspace/stem/tools/card-layouts/tools/render_card.py .
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```
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