System Device Configuration

Functions for system and clock setup available in system_<device>.c. More...

Modules
	Interrupt and Exception Handling
	Functions for interrupt, exception handle available in system_<device>.c.

Functions
void	SystemCoreClockUpdate (void)
	Function to update the variable SystemCoreClock. More...
void	SystemInit (void)
	Function to Initialize the system. More...
void	SystemBannerPrint (void)
	Banner Print for HummingBird SDK. More...
int32_t	Core_Register_IRQ (uint32_t irqn, void *handler)
	Register a riscv core interrupt and register the handler. More...
int32_t	PLIC_Register_IRQ (uint32_t source, uint8_t priority, void *handler)
	Register a specific plic interrupt and register the handler. More...

Variables
uint32_t	SystemCoreClock = SYSTEM_CLOCK
	Variable to hold the system core clock value. More...

Detailed Description

Functions for system and clock setup available in system_<device>.c.

HummingBird provides a template file system_Device.c that must be adapted by the silicon vendor to match their actual device. As a minimum requirement, this file must provide:

• A device-specific system configuration function, SystemInit.
• A global variable that contains the system frequency, SystemCoreClock.
• Global c library _premain_init and _postmain_fini functions called right before and after calling main function.
• Vendor customized interrupt, exception handling code, see Interrupt and Exception Handling

The file configures the device and, typically, initializes the oscillator (PLL) that is part of the microcontroller device. This file might export other functions or variables that provide a more flexible configuration of the microcontroller system.

And this file also provided common interrupt, exception exception handling framework template, Silicon vendor can customize these template code as they want.

Note

Please pay special attention to the static variable SystemCoreClock. This variable might be used throughout the whole system initialization and runtime to calculate frequency/time related values. Thus one must assure that the variable always reflects the actual system clock speed.

Attention

Be aware that a value stored to SystemCoreClock during low level initializaton (i.e. SystemInit()) might get overwritten by C libray startup code and/or .bss section initialization. Thus its highly recommended to call SystemCoreClockUpdate at the beginning of the user main() routine.

Function Documentation

Core_Register_IRQ()

int32_t Core_Register_IRQ	(	uint32_t	irqn,
		void *	handler
	)

Register a riscv core interrupt and register the handler.

This function set interrupt handler for core interrupt

Parameters

[in]	irqn	interrupt number
[in]	handler	interrupt handler, if NULL, handler will not be installed

Returns

-1 means invalid input parameter. 0 means successful.

Remarks

• This function use to configure riscv core interrupt and register its interrupt handler and enable its interrupt.

Definition at line 399 of file system_hbird.c.

{
    if ((irqn > 10)) {
        return -1;
    }
 
    if (handler != NULL) {
        /* register interrupt handler entry to core handlers */
        Interrupt_Register_CoreIRQ(irqn, (unsigned long)handler);
    }
    switch (irqn) {
        case SysTimerSW_IRQn:
            __enable_sw_irq();
            break;
        case SysTimer_IRQn:
            __enable_timer_irq();
            break;
        default:
            break;
    }
 
    return 0;
}

References __enable_sw_irq(), __enable_timer_irq(), Interrupt_Register_CoreIRQ(), SysTimer_IRQn, and SysTimerSW_IRQn.

PLIC_Register_IRQ()

int32_t PLIC_Register_IRQ	(	uint32_t	source,
		uint8_t	priority,
		void *	handler
	)

Register a specific plic interrupt and register the handler.

This function set priority and handler for plic interrupt

Parameters

[in]	source	interrupt source
[in]	priority	interrupt priority
[in]	handler	interrupt handler, if NULL, handler will not be installed

Returns

-1 means invalid input parameter. 0 means successful.

Remarks

• This function use to configure specific plic interrupt and register its interrupt handler and enable its interrupt.

Definition at line 435 of file system_hbird.c.

{
    if ((source >= __PLIC_INTNUM)) {
        return -1;
    }
 
    /* set interrupt priority */
    PLIC_SetPriority(source, priority);
    if (handler != NULL) {
        /* register interrupt handler entry to external handlers */
        Interrupt_Register_ExtIRQ(source, (unsigned long)handler);
    }
    /* enable interrupt */
    PLIC_EnableInterrupt(source);
    __enable_ext_irq();
    return 0;
}

References __enable_ext_irq(), Interrupt_Register_ExtIRQ(), PLIC_EnableInterrupt(), and PLIC_SetPriority().

SystemBannerPrint()

void SystemBannerPrint

(

void

)

Banner Print for HummingBird SDK.

Definition at line 378 of file system_hbird.c.

{
#if defined(HBIRD_BANNER) && (HBIRD_BANNER == 1)
    printf("HummingBird SDK Build Time: %s, %s\r\n", __DATE__, __TIME__);
#ifdef DOWNLOAD_MODE_STRING
    printf("Download Mode: %s\r\n", DOWNLOAD_MODE_STRING);
#endif
    printf("CPU Frequency %lu Hz\r\n", SystemCoreClock);
#endif
}

References SystemCoreClock.

SystemCoreClockUpdate()

void SystemCoreClockUpdate

(

void

)

Function to update the variable SystemCoreClock.

Updates the variable SystemCoreClock and must be called whenever the core clock is changed during program execution. The function evaluates the clock register settings and calculates the current core clock.

Definition at line 101 of file system_hbird.c.

{
    /* ToDo: add code to calculate the system frequency based upon the current
     *    register settings.
     * Note: This function can be used to retrieve the system core clock frequeny
     *    after user changed register settings.
     */
    SystemCoreClock = SYSTEM_CLOCK;
}

References SystemCoreClock.

SystemInit()

void SystemInit

(

void

)

Function to Initialize the system.

Initializes the microcontroller system. Typically, this function configures the oscillator (PLL) that is part of the microcontroller device. For systems with a variable clock speed, it updates the variable SystemCoreClock. SystemInit is called from the file startup_device.

Definition at line 119 of file system_hbird.c.

{
    /* ToDo: add code to initialize the system
     * Warn: do not use global variables because this function is called before
     * reaching pre-main. RW section maybe overwritten afterwards.
     */
    SystemCoreClock = SYSTEM_CLOCK;
}

References SystemCoreClock.

Variable Documentation

SystemCoreClock

uint32_t SystemCoreClock = SYSTEM_CLOCK

Variable to hold the system core clock value.

Holds the system core clock, which is the system clock frequency supplied to the SysTick timer and the processor core clock. This variable can be used by debuggers to query the frequency of the debug timer or to configure the trace clock speed.

Attention

Compilers must be configured to avoid removing this variable in case the application program is not using it. Debugging systems require the variable to be physically present in memory so that it can be examined to configure the debugger.

Definition at line 88 of file system_hbird.c.

Referenced by SystemBannerPrint(), SystemCoreClockUpdate(), and SystemInit().