Register Abbreviations; Gpio Main Features - ST STM32 Application Note

AN4899
2.2

Register abbreviations

The following abbreviations are used in register descriptions (x = A to H):
GPIOx_MODER:
GPIOx_OTYPER:
GPIOx_OSPEEDR:
GPIOx_PUPDR:
GPIOx_IDR:
GPIOx_ODR:
GPIOx_BSRR:
GPIOx_LCKR:
GPIOx_AFRL:
GPIOx_AFRH:
GPIOx_ASCR:
3

GPIO main features

STM32 GPIO exhibits the following features:
•
Output states: push-pull, or open drain + pull-up / pull-down according to
GPIOx_MODER, GPIOx_OTYPER, and GPIOx_PUPDR registers settings
•
Output data from output data register GPIOx_ODR or peripheral (alternate function
output)
•
Speed selection for each I/O (GPIOx_OSPEEDR)
•
Input states: floating, pull-up / pull-down, analog according to GPIOx_MODER,
GPIOx_PUPDR and GPIOx_ASCR registers settings
•
Input data to input data register (GPIOx_IDR) or peripheral (alternate function input)
•
Bit set and reset register (GPIOx_ BSRR) for bitwise write access to GPIOx_ODR
•
Locking mechanism (GPIOx_LCKR) provided to freeze the I/O port configurations
•
Analog function selection registers (GPIOx_MODER and GPIOx_ASCR)
•
Alternate function selection registers (GPIOx_MODER, GPIOx_AFRL, and
GPIOx_AFRH)
• Fast toggle capable of changing every two clock cycles
•
Highly flexible pin multiplexing allowing the use of I/O pins as GPIO or as one of
several peripheral functions
GPIO port mode register
GPIO output type register
GPIO output speed register
GPIO port pull-up / pull-down register
GPIO port input data register
GPIO port output data register
GPIO port bit set / reset register
GPIO port configuration lock register
GPIO alternate function low register
GPIO alternate function high register
GPIO port analog switch control register
AN4899 Rev 3
GPIO main features
7/31
30