问stm32f4将16位写入两个8位gpio端口

EN

wtite_bits(uint16_t cmd)
{
    uint32_t data = GPIOA -> ODR;

    data &= ~(0x1fff);
    data |= cmd & 0x1fff;
    GPIOA -> ODR = data;

    data = GPIOB -> ODR;
    data &= ~(0x0007);
    data |= (cmd & 0x8fff) >> 13;
    GPIOB -> ODR = data;
}

void LCD_write_command(uint16_t cmd) {
   *(volatile uint8_t *)&GPIOD->ODR = cmd & 0xff;
   *(volatile uint8_t *)&GPIOA->ODR = cmd >> 8; //msb
}

void LCD_write_command(uint16_t cmd) {
    GPIOB->BRR = LCD_CS;       // LCD_CS low (chip select pull)
    GPIOB->BRR = LCD_RS;       // LCD_RS low (register select = instruction)
    //GPIOA->ODR = cmd;         // put cmd to PortA (full length)
    // put cmd [0..12] bits to PortA (actual LCD_DB00..LCD_DB12)
    // put cmd [13..15] bits to PortB (actual LCD_DB13..LCD_DB15)
    GPIOA->ODR = cmd & 0x1fff;
    GPIOB->ODR = (GPIOB->ODR & 0xfff8) | (cmd >> 13);
    GPIOB->BRR = LCD_WR;       // pull LCD_WR to low (write strobe start)
    // Write strobe 66ns long by datasheet. GPIO speed on STM32F103 at 72MHz slower -> delay is unnecessary
    // asm volatile ("nop");
    GPIOB->BSRR = LCD_WR;      // pull LCD_WR to high (write strobe end)
    GPIOB->BSRR = LCD_CS;      // LCD_CS high (chip select release)
}