Following on from the previous article that talked about the ECLIC in the GD32VF103 RISC-V microcontroller I decided to measure its interrupt response. The example works like this: Configure a port pin to generate an interrupt when it goes through a high-low transition. The interrupt handler then drives the pin back high again.
The main body of this example consists of a loop which drives the pin low thus triggering an interrupt. The interrupt handler sends it high again. This is done in a loop which incorporates a small delay to facilitate measurement. The GPIO pin in question is Port C bit 13 which happens to control the red LED on the Sipeed Longan Nano. The results are shown in the figure below.
As can be seen, it takes 416.667ns to drive the pin high again. This corresponds to 45 clock cycles at 108Mhz which is the time it takes to save the CPU registers, determine the cause of the interrupt, jump to the handler and perform a standard function entry prologue (set up stack etc). Not too shabby đŸ™‚
