(X = A; Gpio Register Map; Table 32. Gpio Register Map And Reset Values - ST STM32F40 Series Reference Manual

General-purpose I/Os (GPIO)
Bits 31:0 AFRLy: Alternate function selection for port x bit y (y = 0..7)
7.4.10 GPIO alternate function high register (GPIOx_AFRH)
(x = A..I)
Address offset: 0x24
Reset value: 0x0000 0000
31 30 29
AFRH15[3:0]
rw rw rw
15 14 13
AFRH11[3:0]
rw rw rw
Bits 31:0 AFRHy: Alternate function selection for port x bit y (y = 8..15)
These bits are written by software to configure alternate function I/Os
AFRHy selection:
0000: AF0
0001: AF1
0010: AF2
0011: AF3
0100: AF4
0101: AF5
0110: AF6
0111: AF7
7.4.11

GPIO register map

The following table gives the GPIO register map and the reset values.
Table 32. GPIO register map and reset values
Offset Register
GPIOA_MODER
0x00
Reset value 1
203/1422
These bits are written by software to configure alternate function I/Os
AFRLy selection:
0000: AF0
0001: AF1
0010: AF2
0011: AF3
0100: AF4
0101: AF5
0110: AF6
0111: AF7
28 27 26 25
AFRH14[3:0]
rw rw rw rw
12 11 10 9
AFRH10[3:0]
rw rw rw rw
0 1 0 1 0 0 0 0
Doc ID 018909 Rev 4
1000: AF8
1001: AF9
1010: AF10
1011: AF11
1100: AF12
1101: AF13
1110: AF14
1111: AF15
24 23 22
AFRH13[3:0]
rw rw rw
8 7 6
AFRH9[3:0]
rw rw rw
1000: AF8
1001: AF9
1010: AF10
1011: AF11
1100: AF12
1101: AF13
1110: AF14
1111: AF15
0 0 0 0 0 0 0 0 0
21 20 19 18
AFRH12[3:0]
rw rw rw rw
5 4 3 2
AFRH8[3:0]
rw rw rw rw
0 0 0 0 0 0 0 0
RM0090
17 16
rw rw
1 0
rw rw
0 0 0 0 0 0