STMicroelectronics STM32F405 Reference Manual page 172

Reset and clock control for STM32F42xxx and STM32F43xxx (RCC)
Bit 5 GPIOFRST: IO port F reset
Bit 4 GPIOERST: IO port E reset
Bit 3 GPIODRST: IO port D reset
Bit 2 GPIOCRST: IO port C reset
Bit 1 GPIOBRST: IO port B reset
Bit 0 GPIOARST: IO port A reset
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This bit is set and cleared by software.
0: does not reset IO port F
1: resets IO port F
This bit is set and cleared by software.
0: does not reset IO port E
1: resets IO port E
This bit is set and cleared by software.
0: does not reset IO port D
1: resets IO port D
This bit is set and cleared by software.
0: does not reset IO port C
1: resets IO port C
This bit is set and cleared by software.
0: does not reset IO port B
1:resets IO port B
This bit is set and cleared by software.
0: does not reset IO port A
1: resets IO port A
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