Porting FreeRTOS to WCH CH32V307, It seems WCH has some serious issue about their RISC-V MCUs...
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The "PFIC" WCH has made is much alike the ones in Cortex-M, utilizing 0b11 MODE bit and BASE as vector table base address, the absolute addresses point to the handlers are stored based on a pre-defined number. Also, this "PFIC" supports nested interrupt handling and preemption. The vector table looks like the following:
What we can clearly tell from the picture above is WCH does not handle exceptions and interrupts seperately.. The ecall exceptions are fitted in the vector table, and will be vectored if the MODE bit set to 0b01 or 0b11...
The spec clearly described that only [Asynchronous interrupts] should be vectored, not exceptions...