GPIOB->CRH&=0XFFFFFF0F;GPIOB->CRH|=3<<4

这是一段针对STM32系列单片机中GPIOB的寄存器操作代码。具体来说，这段代码将GPIOB的CRH寄存器的第4位到第7位清零，然后将第4位和第5位设置为1，即将GPIOB的8号引脚配置为复用推挽输出模式。简单来说，这段代码的作用是配置GPIOB的8号引脚为输出模式，可以通过该引脚向外部设备输出信号。

相关问题

GPIOB->CRH&=0XFFFFFF0F;GPIOB->CRH|=8<<4

这段代码是针对STM32系列单片机的，作用是将GPIOB的第4个引脚配置为输出模式，输出速率为最高速率50MHz。

具体来说，GPIOB是一个GPIO端口的指针，通过->符号调用该端口的寄存器。CRH是GPIOB的控制寄存器高位，用来配置GPIOB的8个引脚，每个引脚占用4个bit位。因此，&=0XFFFFFF0F用来清除第4个引脚的配置，保留其他引脚的配置；|=8<<4用来将第4个引脚的配置设置为输出模式，最高速率50MHz。其中，8表示输出模式，<<4表示将8左移4位，即将8的二进制码00001000左移4位得到10000000，即第4个bit位为1，表示该引脚为输出模式。

综上所述，这段代码的作用是将GPIOB的第4个引脚配置为输出模式，输出速率为最高速率50MHz。

GPIOB->CRH&=0XFFFFFF0F;GPIOB->CRH|=8<<12;怎么配置

GPIOB->CRH refers to the configuration register high of the GPIOB port. It is a 32-bit register that is used to configure the behavior of the pins of the GPIOB port. Each pin of the port has 4 bits in this register which are used to configure the pin mode, output type, speed, and pull-up/pull-down resistors.

The CRH register is used for the pins 8 to 15 of the GPIOB port, while the CRL register is used for the pins 0 to 7. The configuration of the pins can be set using bitwise operations and constants defined in the STM32F103xx.h header file.

For example, to set pin 12 of GPIOB as an output pin with a maximum output speed of 50 MHz, the following code can be used:

GPIOB->CRH |= GPIO_CRH_MODE12; // Set pin 12 as output
GPIOB->CRH |= GPIO_CRH_CNF12_1; // Set pin 12 as push-pull output
GPIOB->CRH |= GPIO_CRH_MODE12_1; // Set pin 12 to maximum output speed of 50 MHz

Note that this code assumes that the GPIOB clock has already been enabled and that the appropriate pins have been configured as GPIO pins using the GPIOB->CRL register.