Cut and paste this URL to share the unmodified register and value:
https://regviz.com/r/Keil/AT32F423xx_v2/GPIOA/MUXL#0x0
GPIO muxing function low register
GPIOx pin 0 muxing
GPIOx pin 1 muxing
GPIOx pin 2 muxing
GPIOx pin 3 muxing
GPIOx pin 4 muxing
GPIOx pin 5 muxing
GPIOx pin 6 muxing
GPIOx pin 7 muxing
https://github.com/cmsis-svd/cmsis-svd-data