STMicroelectronics STM32F05 series Reference Manual page 137

RM0091
Bits 31:16 Reserved, must be kept at reset value.
Bits 15:0 EXTIx[3:0]: EXTI x configuration bits (x = 0 to 3)
Note: Some of the I/O pins mentioned in the above register may not be available on small
packages.
These bits are written by software to select the source input for the EXTIx
external interrupt. x000: PA[x] pin
x001: PB[x] pin
x010: PC[x] pin
x011: PD[x] pin
x100: reserved
x101: PF[x] pin
other configurations: reserved
Doc ID 018940 Rev 1
System configuration controller (SYSCFG)
137/742