PORT "Chapter 12 Port Control and Interrupts (PORT)" 管脚控制与中断

关于管脚复用（PTC0复用GPIO）官方库：

PORT_SetPinMux(PORTC, 0U, kPORT_MuxAsGpio);
<fsl_port.h>
/*! @brief Pin mux selection */
typedef enum _port_mux
{
	kPORT_PinDisabledOrAnalog = 0U, /*!< Corresponding pin is disabled, but is used as an analog pin. */
	kPORT_MuxAsGpio = 1U,           /*!< Corresponding pin is configured as GPIO. */
	kPORT_MuxAlt2 = 2U,             /*!< Chip-specific */
	kPORT_MuxAlt3 = 3U,             /*!< Chip-specific */
	kPORT_MuxAlt4 = 4U,             /*!< Chip-specific */
	kPORT_MuxAlt5 = 5U,             /*!< Chip-specific */
	kPORT_MuxAlt6 = 6U,             /*!< Chip-specific */
	kPORT_MuxAlt7 = 7U,             /*!< Chip-specific */
	kPORT_MuxAlt8 = 8U,             /*!< Chip-specific */
	kPORT_MuxAlt9 = 9U,             /*!< Chip-specific */
	kPORT_MuxAlt10 = 10U,           /*!< Chip-specific */
	kPORT_MuxAlt11 = 11U,           /*!< Chip-specific */
	kPORT_MuxAlt12 = 12U,           /*!< Chip-specific */
	kPORT_MuxAlt13 = 13U,           /*!< Chip-specific */
	kPORT_MuxAlt14 = 14U,           /*!< Chip-specific */
	kPORT_MuxAlt15 = 15U,           /*!< Chip-specific */
} port_mux_t;
/*!
 * @brief Configures the pin muxing.
 *
 * @param base  PORT peripheral base pointer.
 * @param pin   PORT pin number.
 * @param mux   pin muxing slot selection.
 *        - #kPORT_PinDisabledOrAnalog: Pin disabled or work in analog function.
 *        - #kPORT_MuxAsGpio          : Set as GPIO.
 *        - #kPORT_MuxAlt2            : chip-specific.
 *        - #kPORT_MuxAlt3            : chip-specific.
 *        - #kPORT_MuxAlt4            : chip-specific.
 *        - #kPORT_MuxAlt5            : chip-specific.
 *        - #kPORT_MuxAlt6            : chip-specific.
 *        - #kPORT_MuxAlt7            : chip-specific.
 * @Note : This function is NOT recommended to use together with the PORT_SetPinsConfig, because
 *         the PORT_SetPinsConfig need to configure the pin mux anyway (Otherwise the pin mux is
 *         reset to zero : kPORT_PinDisabledOrAnalog).
 *        This function is recommended to use to reset the pin mux
 *
 */
static inline void PORT_SetPinMux(PORT_Type *base, uint32_t pin, port_mux_t mux)
{
	base->PCR[pin] = (base->PCR[pin] & ~PORT_PCR_MUX_MASK) | PORT_PCR_MUX(mux);
}
<MKV58F24.h>
#define PORT_PCR_MUX_MASK                        (0xF00U)
#define PORT_PCR_MUX_SHIFT                       (8U)
#define PORT_PCR_MUX(x)                          (((uint32_t)(((uint32_t)(x)) << PORT_PCR_MUX_SHIFT)) & PORT_PCR_MUX_MASK)

/** PORT - Register Layout Typedef */
typedef struct {
  __IO uint32_t PCR[32];                           /**< Pin Control Register n, array offset: 0x0, array step: 0x4 */
  __O  uint32_t GPCLR;                             /**< Global Pin Control Low Register, offset: 0x80 */
  __O  uint32_t GPCHR;                             /**< Global Pin Control High Register, offset: 0x84 */
	   uint8_t RESERVED_0[24];
  __IO uint32_t ISFR;                              /**< Interrupt Status Flag Register, offset: 0xA0 */
	   uint8_t RESERVED_1[28];
  __IO uint32_t DFER;                              /**< Digital Filter Enable Register, offset: 0xC0 */
  __IO uint32_t DFCR;                              /**< Digital Filter Clock Register, offset: 0xC4 */
  __IO uint32_t DFWR;                              /**< Digital Filter Width Register, offset: 0xC8 */
} PORT_Type;

PORT分多个通道，PORTA~PORTE，
每个通道寄存器按地址顺序为PCR0~PCR31，GPCLR，GPCHR，ISFR，DFER，DFCR，DFWR，
注意ISFR前后均有一段不使用的空间。
数字滤波寄存器DFER、DFCR、DFWR仅PORTD有效。
每个PCR长32bits，第8到第11位为复用控制，0000为管脚禁用，0001为ALT1（GPIO），其后0010为ALT2以此类推只ALT15（基本上也没有一个管脚能有15个功能，具体参考管脚复用表）
PORT_PCR_MUX完成了左移八位的功能（PORT_PCR_MUX_SHIFT）以达到第八位复用控制寄存器。

龙邱GPIO库中：

void GPIO_Init (GPIO_Type* port, int index, GPIO_CFG dir,int data)
PORT_MemMapPtr p;
switch((u32)port)
{
case 0x400FF000u:
	p = PORTA;
	break;
case 0x400FF040u:
	p = PORTB;
	break;
case 0x400FF080u:
	p = PORTC;
	break;
case 0x400FF0C0u:
	p = PORTD;
	break;
case 0x400FF100u:
	p = PORTE;
	break;
default:
	break;
}
PORT_PCR_REG(p,index)=PORT_PCR_MUX(1);

<MKV58F24.h>
#define PORT_PCR_REG(base,index)                 ((base)->PCR[index])

利用了宏完成了PORT复用操作，PORT_PCR_MUX(1)直接调用官方库，指定了GPIO（ALT1）复用方式

关于外部中断标志
DMA请求会自动清除标志，此外需手动清除。
清除方式是在ISFR中对应位“写入”逻辑1，而不是将其清0。