开发环境：
IDE：MKD 5.30
开发板：RA-Eco-RA4M2
MCU：R7FA4M2AD3CFP
上一章通过控制GPIO的高低电平实现了流水灯，但只是告诉了大家怎么做，如何实现流水灯，本文将深入剖析的GPIO流水灯的前生今世，深入研究流水灯的调用逻辑和数据结构。
前面一章大概讲解GPIO流水灯，关于GPIO的内容很多，具体请参看《RA4M2 Group User’s Manual Hardware》中I/O Ports相关的章节吧。
要想控制LED亮灭，就需要做以上三件事：使能时钟，配置GPIO参数，最后循环控制GPIO的高低电平就能实现流水灯的效果，GPIO的寄存器这里就不说了，更多详细的寄存器描述看官方手册就行，下面先来看看RA4M2的时钟。
时钟是整个处理器运行的基础，时钟信号推动处理器内各个部分执行相应的指令。时钟系统就是CPU的脉搏，决定CPU速率，像人的心跳一样 只有有了心跳，人才能做其他的事情，而单片机有了时钟，才能够运行执行指令，才能够做其他的处理 (点灯，串口，ADC)，时钟的重要性不言而喻。
RA4M2相对Cortex-3内核系列的MCU更为复杂，不仅是外设非常多，就连时钟来源就有8个之多。但我们实际使用的时候只会用到有限的几个外设，使用任何外设都需要时钟才能启动，但并不是所有的外设都需要系统时钟那么高的频率，为了兼容不同速度的设备，有些高速，有些低速，如果都用高速时钟，势必造成浪费，而且，同一个威廉希尔官方网站 ，时钟越快功耗越快，同时抗电磁干扰能力也就越弱，所以较为复杂的MCU都是采用多时钟源的方法来解决这些问题，因此便有了RA4M2的时钟系统和时钟树。
RA4M2不同的时钟源可以用来驱动系统时钟(SCK)：
● MOSC(Main Clock Oscillator)：主时钟振荡器，连接外部 8 ~ 24 MHz 高速晶振
● SOSC(Sub-Clock Oscillator)：副时钟振荡器，连接外部 32.768 kHz 低速晶振(高速外部时钟信号)
● HOCO(High-speed on-chip oscillator)：高速片上振荡器，振荡频率: 16/18/20 MHz
● MOCO(Middle-speed on-chip oscillator)：中速片上振荡器，振荡频率: 8 MHz
● LOCO(Low-speed on-chip oscillator)：低速片上振荡器，振荡频率: 32.768 kHz
● PLL(Phase Locked Loop): 锁相环时钟，可以对输入时钟进行分频和倍频的功能，PLL 输出频率：100 MHz ~ 200 MHz，PLL2 输出频率：120 MHz ~ 240 MHz
RA4M2有两个二级时钟源：
● IWDTLOCO(IWDT-dedicated clock) ：IWDT专用片上振荡器，振荡频率: 15 kHz
● TCK/SWCLK(External clock input for JTAG/ External clock input for SWD) ：JTAG/SWD的外部时钟输入，振荡频率: 最大25MHz
每个时钟源在不使用时都可以单独被打开或关闭，这样就可以优化系统功耗。
RA4M2芯片为了实现低功耗，设计了一个功能完善但却非常复杂的时钟系统。普通的MCU 一般只要配置好 GPIO 的寄存器就可以使用了，但 RA4M2还有一个步骤，就是开启外设时钟。
在 RA4M2中，系统时钟源有很多，从来源可分为外部时钟源和内部时钟源，外部时钟源就是从外部通过接晶振的方式获取时钟源，其中 XTAL、XCIN和TCK/SWCLK是外部时钟源，其他的是内部时钟源。
下面我们看看RA4M2的系统时钟源，我们讲解顺序是按图中红圈标示的顺序：
MOSC是高速外部时钟，可接石英/陶瓷谐振器，或者接外部时钟源，频率范围为8MHz~24MHz。我们的开发板接的是24M的晶振。
SOSC是副时钟振荡器，接频率为 32.768kHz 的石英晶体。这个主要是 RTC 的时钟源。
HOCO是高速内部时钟，高速片上振荡器，振荡频率: 16/18/20 MHz。
MOCO是中速片上振荡器，振荡频率为8 MHz。
LOCO是低速片上振荡器，振荡频率为32.768 kHz。
PLL 为锁相环倍频输出，其时钟输入源可选择为MOSC、HOCO。倍频可选择为10~30倍，但是PLL输出频率最大不得超过 200MHz，PLL2输出频率最大不得超过 240MHz。
图中我们用 A~C标示就是系统时钟进过系统时钟主要流向的地方。
A. 此处是FCLK，最高50MHz.
B. B处就是 RA4M2的系统时钟 ICLK，它是供 RA4M2内核中绝大部分部件工作的时钟源，分别是CPU、DMAC、DTC、闪存 和 SRAM。系统时钟可选择HCOC、MCOC、LOCO、XTAL、SUBCLK、PLL作为时钟源。系统时钟最大频率为 100MHz，当然你也可以超频，不过一般情况为了系统稳定性是没有必要冒风险去超频的。
C. 这里的C处是大部分外设的时钟输入源了。从时钟图上可以看出，其他所有外设的时钟最终来源都是 SCK。SCK 通过分频器分频后送给各模块使用。
主频的时钟为默认的 200 MHz，来源是MOSC的24MHz时钟，经过PLL倍频，流向系统时钟。详细请查看RA Smart Configurator文件的配置。
当系统复位后就会进入Reset_Handler() -> SystemInit() -> bsp_clock_init()，bsp_clock_init()函数就是整个系统时钟的初始化部分，重点看这里，代码如下：
[文件路径: ra\fsp\src\bsp\mcu\all\bsp_clocks.c]
/*******************************************************************************************************************//**
* Initializes system clocks. Makes no assumptions about current register settings.
**********************************************************************************************************************/
void bsp_clock_init (void)
{
/* Unlock CGC and LPM protection registers. */
R_SYSTEM->PRCR = (uint16_t) BSP_PRV_PRCR_UNLOCK;
#if BSP_FEATURE_BSP_FLASH_CACHE
#if !BSP_CFG_USE_LOW_VOLTAGE_MODE && BSP_FEATURE_BSP_FLASH_CACHE_DISABLE_OPM
/* Disable flash cache before modifying MEMWAIT, SOPCCR, or OPCCR. */
R_BSP_FlashCacheDisable();
#else
/* Enable the flash cache and don't disable it while running from flash. On these MCUs, the flash cache does not
* need to be disabled when adjusting the operating power mode. */
R_BSP_FlashCacheEnable();
#endif
#endif
#if BSP_FEATURE_BSP_FLASH_PREFETCH_BUFFER
/* Disable the flash prefetch buffer. */
R_FACI_LP->PFBER = 0;
#endif
bsp_clock_freq_var_init();
#if BSP_CLOCK_CFG_MAIN_OSC_POPULATED
#if BSP_CFG_STARTUP_CLOCK_REG_NOT_RESET
/* Update the main oscillator drive, source, and wait states if the main oscillator is stopped. If the main
* oscillator is running, the drive, source, and wait states are assumed to be already set appropriately. */
if (R_SYSTEM->MOSCCR)
{
/* Don't write to MOSCWTCR unless MOSTP is 1 and MOSCSF = 0. */
FSP_HARDWARE_REGISTER_WAIT(R_SYSTEM->OSCSF_b.MOSCSF, 0U);
/* Configure main oscillator drive. */
R_SYSTEM->MOMCR = BSP_PRV_MOMCR;
/* Set the main oscillator wait time. */
R_SYSTEM->MOSCWTCR = (uint8_t) BSP_CLOCK_CFG_MAIN_OSC_WAIT;
}
#else
/* Configure main oscillator drive. */
R_SYSTEM->MOMCR = BSP_PRV_MOMCR;
/* Set the main oscillator wait time. */
R_SYSTEM->MOSCWTCR = (uint8_t) BSP_CLOCK_CFG_MAIN_OSC_WAIT;
#endif
#endif
#if BSP_FEATURE_CGC_HAS_SOSC
#if BSP_CLOCK_CFG_SUBCLOCK_POPULATED
/* If Sub-Clock Oscillator is started at reset, stop it before configuring the subclock drive. */
if (0U == R_SYSTEM->SOSCCR)
{
/* Stop the Sub-Clock Oscillator to update the SOMCR register. */
R_SYSTEM->SOSCCR = 1U;
/* Allow a stop interval of at least 5 SOSC clock cycles before configuring the drive capacity
* and restarting Sub-Clock Oscillator. */
R_BSP_SoftwareDelay(BSP_PRV_SUBCLOCK_STOP_INTERVAL_US, BSP_DELAY_UNITS_MICROSECONDS);
}
/* Configure the subclock drive as subclock is not running. */
R_SYSTEM->SOMCR = ((BSP_CLOCK_CFG_SUBCLOCK_DRIVE << BSP_FEATURE_CGC_SODRV_SHIFT) & BSP_FEATURE_CGC_SODRV_MASK);
/* Restart the Sub-Clock Oscillator. */
R_SYSTEM->SOSCCR = 0U;
#if (BSP_CLOCKS_SOURCE_CLOCK_SUBCLOCK == BSP_CFG_CLOCK_SOURCE) || (BSP_PRV_HOCO_USE_FLL)
/* If the subclock is the system clock source OR if FLL is used, wait for stabilization. */
R_BSP_SubClockStabilizeWait(BSP_CLOCK_CFG_SUBCLOCK_STABILIZATION_MS);
#endif
#else
R_SYSTEM->SOSCCR = 1U;
#endif
#endif
#if BSP_FEATURE_CGC_HAS_HOCOWTCR
#if BSP_FEATURE_CGC_HOCOWTCR_64MHZ_ONLY
/* These MCUs only require writes to HOCOWTCR if HOCO is set to 64 MHz. */
#if 64000000 == BSP_HOCO_HZ
#if BSP_CFG_USE_LOW_VOLTAGE_MODE
/* Wait for HOCO to stabilize before writing to HOCOWTCR. */
FSP_HARDWARE_REGISTER_WAIT(R_SYSTEM->OSCSF_b.HOCOSF, 1U);
#else
/* HOCO is assumed to be stable because these MCUs also require the HOCO to be stable before changing the operating
* power control mode. */
#endif
R_SYSTEM->HOCOWTCR = BSP_FEATURE_CGC_HOCOWTCR_VALUE;
#endif
#else
/* These MCUs require HOCOWTCR to be set to the maximum value except in snooze mode. There is no restriction to
* writing this register. */
R_SYSTEM->HOCOWTCR = BSP_FEATURE_CGC_HOCOWTCR_VALUE;
#endif
#endif
#if !BSP_CFG_USE_LOW_VOLTAGE_MODE
#if BSP_CFG_STARTUP_CLOCK_REG_NOT_RESET
/* Switch to high-speed to prevent any issues with the subsequent clock configurations. */
bsp_prv_operating_mode_set(BSP_PRV_OPERATING_MODE_HIGH_SPEED);
#elif BSP_FEATURE_CGC_LOW_VOLTAGE_MAX_FREQ_HZ > 0U
/* MCUs that support low voltage mode start up in low voltage mode. */
bsp_prv_operating_mode_opccr_set(BSP_PRV_OPERATING_MODE_HIGH_SPEED);
#if !BSP_PRV_HOCO_USED
/* HOCO must be running during startup in low voltage mode. If HOCO is not used, turn it off after exiting low
* voltage mode. */
R_SYSTEM->HOCOCR = 1U;
#endif
#elif BSP_FEATURE_CGC_STARTUP_OPCCR_MODE != BSP_PRV_OPERATING_MODE_HIGH_SPEED
/* Some MCUs do not start in high speed mode. */
bsp_prv_operating_mode_opccr_set(BSP_PRV_OPERATING_MODE_HIGH_SPEED);
#endif
#endif
/* The FLL function can only be used when the subclock is running. */
#if BSP_PRV_HOCO_USE_FLL
/* If FLL is to be used configure FLLCR1 and FLLCR2 before starting HOCO. */
R_SYSTEM->FLLCR2 = BSP_PRV_FLL_FLLCR2;
R_SYSTEM->FLLCR1 = 1U;
#endif
/* Start all clocks used by other clocks first. */
#if BSP_PRV_HOCO_USED
R_SYSTEM->HOCOCR = 0U;
#if BSP_PRV_HOCO_USE_FLL && (BSP_CLOCKS_SOURCE_CLOCK_HOCO != BSP_CFG_PLL_SOURCE)
/* If FLL is enabled, wait for the FLL stabilization delay (1.8 ms) */
R_BSP_SoftwareDelay(BSP_PRV_FLL_STABILIZATION_TIME_US, BSP_DELAY_UNITS_MICROSECONDS);
#endif
#if BSP_PRV_STABILIZE_HOCO
/* Wait for HOCO to stabilize. */
FSP_HARDWARE_REGISTER_WAIT(R_SYSTEM->OSCSF_b.HOCOSF, 1U);
#endif
#endif
#if BSP_PRV_MOCO_USED
#if BSP_CFG_STARTUP_CLOCK_REG_NOT_RESET
/* If the MOCO is not running, start it and wait for it to stabilize using a software delay. */
if (0U != R_SYSTEM->MOCOCR)
{
R_SYSTEM->MOCOCR = 0U;
#if BSP_PRV_STABILIZE_MOCO
R_BSP_SoftwareDelay(BSP_FEATURE_CGC_MOCO_STABILIZATION_MAX_US, BSP_DELAY_UNITS_MICROSECONDS);
#endif
}
#endif
#endif
#if BSP_PRV_LOCO_USED
#if BSP_CFG_STARTUP_CLOCK_REG_NOT_RESET
/* If the LOCO is not running, start it and wait for it to stabilize using a software delay. */
if (0U != R_SYSTEM->LOCOCR)
{
R_SYSTEM->LOCOCR = 0U;
#if BSP_PRV_STABILIZE_LOCO
R_BSP_SoftwareDelay(BSP_FEATURE_CGC_LOCO_STABILIZATION_MAX_US, BSP_DELAY_UNITS_MICROSECONDS);
#endif
}
#else
R_SYSTEM->LOCOCR = 0U;
#if BSP_PRV_STABILIZE_LOCO
R_BSP_SoftwareDelay(BSP_FEATURE_CGC_LOCO_STABILIZATION_MAX_US, BSP_DELAY_UNITS_MICROSECONDS);
#endif
#endif
#endif
#if BSP_PRV_MAIN_OSC_USED
R_SYSTEM->MOSCCR = 0U;
#if BSP_PRV_STABILIZE_MAIN_OSC
/* Wait for main oscillator to stabilize. */
FSP_HARDWARE_REGISTER_WAIT(R_SYSTEM->OSCSF_b.MOSCSF, 1U);
#endif
#endif
/* Start clocks that require other clocks. At this point, all dependent clocks are running and stable if needed. */
#if BSP_PRV_STARTUP_OPERATING_MODE != BSP_PRV_OPERATING_MODE_LOW_SPEED
#if BSP_FEATURE_CGC_HAS_PLL2 && BSP_CFG_PLL2_SOURCE != BSP_CLOCKS_CLOCK_DISABLED
R_SYSTEM->PLL2CCR = BSP_PRV_PLL2CCR;
#if (3U == BSP_FEATURE_CGC_PLLCCR_TYPE)
R_SYSTEM->PLL2CCR2 = BSP_PRV_PLL2CCR2;
#endif
/* Start PLL2. */
R_SYSTEM->PLL2CR = 0U;
#endif /* BSP_FEATURE_CGC_HAS_PLL2 && BSP_CFG_PLL2_ENABLE */
#endif
#if BSP_PRV_PLL_SUPPORTED && BSP_PRV_PLL_USED
#if BSP_CLOCKS_SOURCE_CLOCK_PLL == BSP_CFG_CLOCK_SOURCE
/* Configure the PLL registers. */
#if 1U == BSP_FEATURE_CGC_PLLCCR_TYPE
R_SYSTEM->PLLCCR = (uint16_t) BSP_PRV_PLLCCR;
#elif 2U == BSP_FEATURE_CGC_PLLCCR_TYPE
R_SYSTEM->PLLCCR2 = (uint8_t) BSP_PRV_PLLCCR;
#elif 3U == BSP_FEATURE_CGC_PLLCCR_TYPE
R_SYSTEM->PLLCCR = (uint16_t) BSP_PRV_PLLCCR;
R_SYSTEM->PLLCCR2 = (uint16_t) BSP_PRV_PLLCCR2;
#endif
#if BSP_FEATURE_CGC_PLLCCR_WAIT_US > 0
/* This loop is provided to ensure at least 1 us passes between setting PLLMUL and clearing PLLSTP on some
* MCUs (see PLLSTP notes in Section 8.2.4 "PLL Control Register (PLLCR)" of the RA4M1 manual R01UH0887EJ0100).
* Five loops are needed here to ensure the most efficient path takes at least 1 us from the setting of
* PLLMUL to the clearing of PLLSTP. HOCO is the fastest clock we can be using here since PLL cannot be running
* while setting PLLCCR. */
bsp_prv_software_delay_loop(BSP_DELAY_LOOPS_CALCULATE(BSP_PRV_MAX_HOCO_CYCLES_PER_US));
#endif
#endif
R_SYSTEM->PLLCR = 0U;
#if BSP_PRV_STABILIZE_PLL
/* Wait for PLL to stabilize. */
FSP_HARDWARE_REGISTER_WAIT(R_SYSTEM->OSCSF_b.PLLSF, 1U);
#endif
#endif
/* Set source clock and dividers. */
#if BSP_CFG_STARTUP_CLOCK_REG_NOT_RESET
#if BSP_TZ_SECURE_BUILD
/* In case of soft reset, make sure callback pointer is NULL initially. */
g_bsp_clock_update_callback = NULL;
#endif
#if BSP_FEATURE_CGC_HAS_CPUCLK
bsp_prv_clock_set(BSP_CFG_CLOCK_SOURCE, BSP_PRV_STARTUP_SCKDIVCR, BSP_PRV_STARTUP_SCKDIVCR2);
#else
bsp_prv_clock_set(BSP_CFG_CLOCK_SOURCE, BSP_PRV_STARTUP_SCKDIVCR, 0);
#endif
#else
bsp_prv_clock_set_hard_reset();
#endif
/* If the MCU can run in a lower power mode, apply the optimal operating speed mode. */
#if !BSP_CFG_USE_LOW_VOLTAGE_MODE
#if BSP_PRV_STARTUP_OPERATING_MODE != BSP_PRV_OPERATING_MODE_HIGH_SPEED
#if BSP_PRV_PLL_SUPPORTED
#if BSP_CFG_STARTUP_CLOCK_REG_NOT_RESET
if (BSP_PRV_OPERATING_MODE_LOW_SPEED == BSP_PRV_STARTUP_OPERATING_MODE)
{
/* If the MCU has a PLL, ensure PLL is stopped and stable before entering low speed mode. */
R_SYSTEM->PLLCR = 1U;
/* Wait for PLL to stabilize. */
FSP_HARDWARE_REGISTER_WAIT(R_SYSTEM->OSCSF_b.PLLSF, 0U);
#if BSP_FEATURE_CGC_HAS_PLL2
/* If the MCU has a PLL2, ensure PLL2 is stopped and stable before entering low speed mode. */
R_SYSTEM->PLL2CR = 1U;
/* Wait for PLL to stabilize. */
FSP_HARDWARE_REGISTER_WAIT(R_SYSTEM->OSCSF_b.PLL2SF, 0U);
#endif
}
#endif
#endif
bsp_prv_operating_mode_set(BSP_PRV_STARTUP_OPERATING_MODE);
#endif
#endif
#if defined(BSP_PRV_POWER_USE_DCDC) && (BSP_PRV_POWER_USE_DCDC == BSP_PRV_POWER_DCDC_STARTUP) && \
(BSP_PRV_STARTUP_OPERATING_MODE <= BSP_PRV_OPERATING_MODE_MIDDLE_SPEED)
/* Start DCDC as part of BSP startup when configured (BSP_CFG_DCDC_ENABLE == 2). */
R_BSP_PowerModeSet(BSP_CFG_DCDC_VOLTAGE_RANGE);
#endif
/* Configure BCLK if it exists on the MCU. */
#ifdef BSP_CFG_BCLK_OUTPUT
#if BSP_CFG_BCLK_OUTPUT > 0U
R_SYSTEM->BCKCR = BSP_CFG_BCLK_OUTPUT - 1U;
R_SYSTEM->EBCKOCR = 1U;
#else
#if BSP_CFG_STARTUP_CLOCK_REG_NOT_RESET
R_SYSTEM->EBCKOCR = 0U;
#endif
#endif
#endif
/* Configure SDRAM clock if it exists on the MCU. */
#ifdef BSP_CFG_SDCLK_OUTPUT
R_SYSTEM->SDCKOCR = BSP_CFG_SDCLK_OUTPUT;
#endif
/* Configure CLKOUT. */
#if BSP_CFG_CLKOUT_SOURCE == BSP_CLOCKS_CLOCK_DISABLED
#if BSP_CFG_STARTUP_CLOCK_REG_NOT_RESET
R_SYSTEM->CKOCR = 0U;
#endif
#else
uint8_t ckocr = BSP_CFG_CLKOUT_SOURCE | (BSP_CFG_CLKOUT_DIV << BSP_PRV_CKOCR_CKODIV_BIT);
R_SYSTEM->CKOCR = ckocr;
ckocr |= (1U << BSP_PRV_CKOCR_CKOEN_BIT);
R_SYSTEM->CKOCR = ckocr;
#endif
#if BSP_PRV_STARTUP_OPERATING_MODE != BSP_PRV_OPERATING_MODE_LOW_SPEED
#if BSP_CFG_UCK_SOURCE != BSP_CLOCKS_CLOCK_DISABLED
/* If the USB clock has a divider setting in SCKDIVCR2. */
#if BSP_FEATURE_BSP_HAS_USB_CLOCK_DIV && !BSP_FEATURE_BSP_HAS_USBCKDIVCR
R_SYSTEM->SCKDIVCR2 = BSP_PRV_UCK_DIV << BSP_PRV_SCKDIVCR2_UCK_BIT;
#endif /* BSP_FEATURE_BSP_HAS_USB_CLOCK_DIV && !BSP_FEATURE_BSP_HAS_USBCKDIVCR */
/* If there is a REQ bit in USBCKCR than follow sequence from section 8.2.29 in RA6M4 hardware manual R01UH0890EJ0050. */
#if BSP_FEATURE_BSP_HAS_USB_CLOCK_REQ
/* Request to change the USB Clock. */
R_SYSTEM->USBCKCR_b.USBCKSREQ = 1;
/* Wait for the clock to be stopped. */
FSP_HARDWARE_REGISTER_WAIT(R_SYSTEM->USBCKCR_b.USBCKSRDY, 1U);
/* Write the settings. */
R_SYSTEM->USBCKDIVCR = BSP_PRV_UCK_DIV;
/* Select the USB Clock without enabling it. */
R_SYSTEM->USBCKCR = BSP_CFG_UCK_SOURCE | R_SYSTEM_USBCKCR_USBCKSREQ_Msk;
#endif /* BSP_FEATURE_BSP_HAS_USB_CLOCK_REQ */
#if BSP_FEATURE_BSP_HAS_USB_CLOCK_SEL
/* Some MCUs use an alternate register for selecting the USB clock source. */
#if BSP_FEATURE_BSP_HAS_USB_CLOCK_SEL_ALT
#if BSP_CLOCKS_SOURCE_CLOCK_PLL == BSP_CFG_UCK_SOURCE
/* Write to USBCKCR to select the PLL. */
R_SYSTEM->USBCKCR_ALT = 0;
#elif BSP_CLOCKS_SOURCE_CLOCK_HOCO == BSP_CFG_UCK_SOURCE
/* Write to USBCKCR to select the HOCO. */
R_SYSTEM->USBCKCR_ALT = 1;
#endif
#else
/* Select the USB Clock. */
R_SYSTEM->USBCKCR = BSP_CFG_UCK_SOURCE;
#endif
#endif /* BSP_FEATURE_BSP_HAS_USB_CLOCK_REQ */
#if BSP_FEATURE_BSP_HAS_USB_CLOCK_REQ
/* Wait for the USB Clock to be started. */
FSP_HARDWARE_REGISTER_WAIT(R_SYSTEM->USBCKCR_b.USBCKSRDY, 0U);
#endif /* BSP_FEATURE_BSP_HAS_USB_CLOCK_REQ */
#endif /* BSP_CFG_USB_ENABLE */
#endif /* BSP_PRV_STARTUP_OPERATING_MODE != BSP_PRV_OPERATING_MODE_LOW_SPEED */
/* Set the OCTASPI clock if it exists on the MCU (See section 8.2.30 of the RA6M4 hardware manual R01UH0890EJ0050). */
#if BSP_FEATURE_BSP_HAS_OCTASPI_CLOCK && BSP_CFG_OCTA_SOURCE != BSP_CLOCKS_CLOCK_DISABLED
bsp_octaclk_settings_t octaclk_settings =
{
.source_clock = (bsp_clocks_source_t) BSP_CFG_OCTA_SOURCE,
.divider = (bsp_clocks_octaclk_div_t) BSP_CFG_OCTA_DIV
};
R_BSP_OctaclkUpdate(&octaclk_settings);
#endif /* BSP_FEATURE_BSP_HAS_OCTASPI_CLOCK && BSP_CFG_OCTASPI_CLOCK_ENABLE */
/* Set the CANFD clock if it exists on the MCU */
#if BSP_FEATURE_BSP_HAS_CANFD_CLOCK && (BSP_CFG_CANFDCLK_SOURCE != BSP_CLOCKS_CLOCK_DISABLED) && \
(BSP_CFG_CANFDCLK_SOURCE != BSP_CLOCKS_SOURCE_CLOCK_MAIN_OSC)
bsp_peripheral_clock_set(&R_SYSTEM->CANFDCKCR,
&R_SYSTEM->CANFDCKDIVCR,
BSP_CFG_CANFDCLK_DIV,
BSP_CFG_CANFDCLK_SOURCE);
#endif
/* Set the SCISPI clock if it exists on the MCU */
#if BSP_FEATURE_BSP_HAS_SCISPI_CLOCK && (BSP_CFG_SCISPICLK_SOURCE != BSP_CLOCKS_CLOCK_DISABLED)
bsp_peripheral_clock_set(&R_SYSTEM->SCISPICKCR,
&R_SYSTEM->SCISPICKDIVCR,
BSP_CFG_SCISPICLK_DIV,
BSP_CFG_SCISPICLK_SOURCE);
#endif
/* Set the SCI clock if it exists on the MCU */
#if BSP_FEATURE_BSP_HAS_SCI_CLOCK && (BSP_CFG_SCICLK_SOURCE != BSP_CLOCKS_CLOCK_DISABLED)
bsp_peripheral_clock_set(&R_SYSTEM->SCICKCR, &R_SYSTEM->SCICKDIVCR, BSP_CFG_SCICLK_DIV, BSP_CFG_SCICLK_SOURCE);
#endif
/* Set the SPI clock if it exists on the MCU */
#if BSP_FEATURE_BSP_HAS_SPI_CLOCK && (BSP_CFG_SPICLK_SOURCE != BSP_CLOCKS_CLOCK_DISABLED)
bsp_peripheral_clock_set(&R_SYSTEM->SPICKCR, &R_SYSTEM->SPICKDIVCR, BSP_CFG_SPICLK_DIV, BSP_CFG_SPICLK_SOURCE);
#endif
/* Set the GPT clock if it exists on the MCU */
#if BSP_FEATURE_BSP_HAS_GPT_CLOCK && (BSP_CFG_GPTCLK_SOURCE != BSP_CLOCKS_CLOCK_DISABLED)
bsp_peripheral_clock_set(&R_SYSTEM->GPTCKCR, &R_SYSTEM->GPTCKDIVCR, BSP_CFG_GPTCLK_DIV, BSP_CFG_GPTCLK_SOURCE);
#endif
/* Set the IIC clock if it exists on the MCU */
#if BSP_FEATURE_BSP_HAS_IIC_CLOCK && (BSP_CFG_IICCLK_SOURCE != BSP_CLOCKS_CLOCK_DISABLED)
bsp_peripheral_clock_set(&R_SYSTEM->IICCKCR, &R_SYSTEM->IICCKDIVCR, BSP_CFG_IICCLK_DIV, BSP_CFG_IICCLK_SOURCE);
#endif
/* Set the I3C clock if it exists on the MCU */
#if BSP_FEATURE_BSP_HAS_I3C_CLOCK && (BSP_CFG_I3CCLK_SOURCE != BSP_CLOCKS_CLOCK_DISABLED)
bsp_peripheral_clock_set(&R_SYSTEM->I3CCKCR, &R_SYSTEM->I3CCKDIVCR, BSP_CFG_I3CCLK_DIV, BSP_CFG_I3CCLK_SOURCE);
#endif
/* Set the ADC clock if it exists on the MCU */
#if BSP_FEATURE_BSP_HAS_ADC_CLOCK && (BSP_CFG_ADCCLK_SOURCE != BSP_CLOCKS_CLOCK_DISABLED)
bsp_peripheral_clock_set(&R_SYSTEM->ADCCKCR, &R_SYSTEM->ADCCKDIVCR, BSP_CFG_ADCCLK_DIV, BSP_CFG_ADCCLK_SOURCE);
#endif
/* Set the LCD clock if it exists on the MCU */
#if BSP_FEATURE_BSP_HAS_LCD_CLOCK && (BSP_CFG_LCDCLK_SOURCE != BSP_CLOCKS_CLOCK_DISABLED)
bsp_peripheral_clock_set(&R_SYSTEM->LCDCKCR, &R_SYSTEM->LCDCKDIVCR, BSP_CFG_LCDCLK_DIV, BSP_CFG_LCDCLK_SOURCE);
#endif
/* Set the USB-HS clock if it exists on the MCU */
#if BSP_FEATURE_BSP_HAS_USBHS_CLOCK && (BSP_CFG_UHSCK_SOURCE != BSP_CLOCKS_CLOCK_DISABLED)
bsp_peripheral_clock_set(&R_SYSTEM->USBHSCKCR, &R_SYSTEM->USBHSCKDIVCR, BSP_CFG_UHSCK_DIV, BSP_CFG_UHSCK_SOURCE);
#endif
/* Lock CGC and LPM protection registers. */
R_SYSTEM->PRCR = (uint16_t) BSP_PRV_PRCR_LOCK;
#if BSP_FEATURE_BSP_FLASH_CACHE && BSP_FEATURE_BSP_FLASH_CACHE_DISABLE_OPM
R_BSP_FlashCacheEnable();
#endif
#if BSP_FEATURE_BSP_FLASH_PREFETCH_BUFFER
R_FACI_LP->PFBER = 1;
#endif
}
其中配置时钟的基地址是R_SYSTEM，定义如下：
#define R_SYSTEM ((R_SYSTEM_Type *) R_SYSTEM_BASE)
可以查看配置时钟的结构体是R_SYSTEM_Type，该结构包含了系统时钟的所有寄存器描述，该结构体非常大，笔者只是截取了部分。
总结下，整个bsp_clock_init()函数的主要工作如下：
Step1：时钟配置准备阶段
Step2：配置系统时钟
Step3：配置BCLK/SDRAM/CLKOUT输出和外设时钟
Step4：锁定CGC和LPM
从在SystemInit ()函数中可以看到，在初始化系统的时钟前后，均调用了R_BSP_WarmStart()函数，其函数原型如下：
[文件路径: src\hal_entry.c]
/*******************************************************************************************************************//**
* This function is called at various points during the startup process. This implementation uses the event that is
* called right before main() to set up the pins.
*
* @param[in] event Where at in the start up process the code is currently at
**********************************************************************************************************************/
void R_BSP_WarmStart (bsp_warm_start_event_t event)
{
if (BSP_WARM_START_RESET == event)
{
#if BSP_FEATURE_FLASH_LP_VERSION != 0
/* Enable reading from data flash. */
R_FACI_LP->DFLCTL = 1U;
/* Would normally have to wait tDSTOP(6us) for data flash recovery. Placing the enable here, before clock and
* C runtime initialization, should negate the need for a delay since the initialization will typically take more than 6us. */
#endif
}
if (BSP_WARM_START_POST_C == event)
{
/* C runtime environment and system clocks are setup. */
/* Configure pins. */
R_IOPORT_Open(&g_ioport_ctrl, g_ioport.p_cfg);
}
}
这里可以看到，在系统时钟初始化后，代码如下：
R_BSP_WarmStart(BSP_WARM_START_POST_CLOCK);
因此，这里就进入了GPIO的配置，核心代码如下：
R_IOPORT_Open(&g_ioport_ctrl,
g_ioport.p_cfg);
g_ioport_ctrl和g_ioport是全局变量，定义如下：
ioport_instance_ctrl_t g_ioport_ctrl;
const ioport_instance_t g_ioport =
{
.p_api = &g_ioport_on_ioport,
.p_ctrl = &g_ioport_ctrl,
.p_cfg = &g_bsp_pin_cfg,
};
而g_ioport又内嵌了g_bsp_pin_cfg，g_bsp_pin_cfg相关的定义如下：
const ioport_pin_cfg_t g_bsp_pin_cfg_data[] = {
{
.pin = BSP_IO_PORT_01_PIN_08,
.pin_cfg = ((uint32_t) IOPORT_CFG_PERIPHERAL_PIN | (uint32_t) IOPORT_PERIPHERAL_DEBUG)
},
{
.pin = BSP_IO_PORT_01_PIN_09,
.pin_cfg = ((uint32_t) IOPORT_CFG_PERIPHERAL_PIN | (uint32_t) IOPORT_PERIPHERAL_DEBUG)
},
{
.pin = BSP_IO_PORT_01_PIN_10,
.pin_cfg = ((uint32_t) IOPORT_CFG_PERIPHERAL_PIN | (uint32_t) IOPORT_PERIPHERAL_DEBUG)
},
{
.pin = BSP_IO_PORT_03_PIN_00,
.pin_cfg = ((uint32_t) IOPORT_CFG_PERIPHERAL_PIN | (uint32_t) IOPORT_PERIPHERAL_DEBUG)
},
{
.pin = BSP_IO_PORT_04_PIN_04,
.pin_cfg = ((uint32_t) IOPORT_CFG_PORT_DIRECTION_OUTPUT | (uint32_t) IOPORT_CFG_PORT_OUTPUT_LOW)
},
{
.pin = BSP_IO_PORT_04_PIN_05,
.pin_cfg = ((uint32_t) IOPORT_CFG_PORT_DIRECTION_OUTPUT | (uint32_t) IOPORT_CFG_PORT_OUTPUT_LOW)
},
{
.pin = BSP_IO_PORT_04_PIN_15,
.pin_cfg = ((uint32_t) IOPORT_CFG_PORT_DIRECTION_OUTPUT | (uint32_t) IOPORT_CFG_PORT_OUTPUT_LOW)
},
};
const ioport_cfg_t g_bsp_pin_cfg = {
.number_of_pins = sizeof(g_bsp_pin_cfg_data)/sizeof(ioport_pin_cfg_t),
.p_pin_cfg_data = &g_bsp_pin_cfg_data[0],
};
从结构体数组g_bsp_pin_cfg_data中可以看到，我们芯配置的3个GPIO端口，在后面的初始时就能将其初始化了。
R_IOPORT_Open()函数的核心是r_ioport_pins_config ()。
[文件路径: ra\fsp\src\r_ioport\r_ioport.c]
/*******************************************************************************************************************//**
* Configures pins.
*
* @param[in] p_cfg Pin configuration data
**********************************************************************************************************************/
void r_ioport_pins_config (const ioport_cfg_t * p_cfg)
{
#if BSP_MCU_VBATT_SUPPORT
/* Handle any VBATT domain pin configuration. */
bsp_vbatt_init(p_cfg);
#endif
uint16_t pin_count;
ioport_cfg_t * p_pin_data;
p_pin_data = (ioport_cfg_t *) p_cfg;
R_BSP_PinAccessEnable(); // Protect PWPR from re-entrancy
for (pin_count = 0U; pin_count < p_pin_data->number_of_pins; pin_count++)
{
r_ioport_pfs_write(p_pin_data->p_pin_cfg_data[pin_count].pin, p_pin_data->p_pin_cfg_data[pin_count].pin_cfg);
}
R_BSP_PinAccessDisable();
}
r_ioport_pins_config ()函数中，根据GPIO的梳数量依次进行初始化。
r_ioport_pfs_write()函数的原型如下：
[文件路径: ra\fsp\src\r_ioport\r_ioport.c]
/*******************************************************************************************************************//**
* Writes to the specified pin's PFS register
*
* @param[in] pin Pin to write PFS data for
* @param[in] value Value to be written to the PFS register
*
**********************************************************************************************************************/
static void r_ioport_pfs_write (bsp_io_port_pin_t pin, uint32_t value)
{
/* PMR bits should be cleared before specifying PSEL. Reference section "20.7 Notes on the PmnPFS Register Setting"
* in the RA6M3 manual R01UH0886EJ0100. */
if ((value & IOPORT_PRV_PERIPHERAL_FUNCTION) > 0)
{
/* Clear PMR */
R_PFS->PORT[pin >> IOPORT_PRV_PORT_OFFSET].PIN[pin & BSP_IO_PRV_8BIT_MASK].PmnPFS_b.PMR = 0;
/* New config with PMR = 0 */
R_PFS->PORT[pin >> IOPORT_PRV_PORT_OFFSET].PIN[pin &
BSP_IO_PRV_8BIT_MASK].PmnPFS =
(value & ~((uint32_t) IOPORT_PRV_PERIPHERAL_FUNCTION));
}
/* Write configuration */
R_PFS->PORT[pin >> IOPORT_PRV_PORT_OFFSET].PIN[pin & BSP_IO_PRV_8BIT_MASK].PmnPFS = value;
}
R_PFS就是GPIO的基地址，定义如下：
#define R_PFS ((R_PFS_Type *) R_PFS_BASE)
这里就是对GPIO 进行初始化操作，包括模式、方向等
到此，基本对时钟和GPIO分析玩了，我想大家已经对RA4M2固件库的逻辑有了一定的认识，从本质上讲，都是在配置寄存器，只是地址和值不同罢了。只是RA4M2的固件库设计比较复杂，可能对于习惯ST的风格，初学者可能会有些不适用，但是其本质是一样的。
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