RM0008 General-purpose and alternate-function I/Os (GPIOs and AFIOs)
Doc ID 13902 Rev 12 165/1096
9.2 GPIO registers
Refer to Section 2.1 on page 46 for a list of abbreviations used in register descriptions.
The peripheral registers have to be accessed by words (32-bit).
9.2.1 Port configuration register low (GPIOx_CRL) (x=A..G)
Address offset: 0x00
Reset value: 0x4444 4444
31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16
CNF7[1:0] MODE7[1:0] CNF6[1:0] MODE6[1:0] CNF5[1:0] MODE5[1:0] CNF4[1:0] MODE4[1:0]
rw rw rw rw rw rw rw rw rw rw rw rw rw rw rw rw
1514131211109876543210
CNF3[1:0] MODE3[1:0] CNF2[1:0] MODE2[1:0] CNF1[1:0] MODE1[1:0] CNF0[1:0] MODE0[1:0]
rw rw rw rw rw rw rw rw rw rw rw rw rw rw rw rw
Bits 31:30, 27:26,
23:22, 19:18, 15:14,
11:10, 7:6, 3:2
CNFy[1:0]: Port x configuration bits (y= 0 .. 7)
These bits are written by software to configure the corresponding I/O port.
Refer to Table 20: Port bit configuration table on page 156.
In input mode (MODE[1:0]=00):
00: Analog mode
01: Floating input (reset state)
10: Input with pull-up / pull-down
11: Reserved
In output mode (MODE[1:0]
> 00):
00: General purpose output push-pull
01: General purpose output Open-drain
10: Alternate function output Push-pull
11: Alternate function output Open-drain
Bits 29:28, 25:24,
21:20, 17:16, 13:12,
9:8, 5:4, 1:0
MODEy[1:0]: Port x mode bits (y= 0 .. 7)
These bits are written by software to configure the corresponding I/O port.
Refer to Table 20: Port bit configuration table on page 156.
00: Input mode (reset state)
01: Output mode, max speed 10 MHz.
10: Output mode, max speed 2 MHz.
11: Output mode, max speed 50 MHz.
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