Xtal is <undefined

XTAL is a virtual register in the µVision simulator that specifies the external clock in MHz. This register is only available if you use our old/deprecated simulator. This knowledgebase article explains how to select this simulator:
https://developer.arm.com/documentation/ka002225/latest/
XTAL is not supported if you use a Fast Model of Fixed Virtual Platform (FVP) within uVision.

What do you want to do?

I want to define STM32F103C8 external clock. It is undefined which is why STM32 is not working correctly.

I still don't know what is not working correctly.

Please remember that XTAL is a virtual register in the µVision simulator. It has no influence on your code and therefore your application.

Dear Hans,

Please see the attached photo. My problem is I want to define my clock frequency in keil uvision but Keil doesn't let me, it shows <undefined>.  For example, I write simple blink code, if I can't choose xtal frequency, it doesn't work correctly. Is there an alternative for choosing xtal frequency in keil uvision? I put the code below.

I want to blink my LED in 1 second.

#include "stm32f10x.h" // Device header

void delay(int rep);

int main(void)
{
RCC->APB2ENR |= 0x10; /// Or 0b10000 --> Anabling Preiph GPIOC
GPIOC->CRH &= 0xFF0FFFFF; /// Reset the PORT C PIN 13
GPIOC->CRH |= 0x00300000; /// Set Port C PIN 13 as Output
GPIOC->ODR |= 0x2000; /// Set Port C Pin 13
while(1)
{
/// Blinking the Port C pin 13
GPIOC->ODR |= 0x2000;
delay(10);
GPIOC->ODR &= ~0x2000;
delay(10);

}

}

/// Random time delay Function
void delay(int rep)
{
for(;rep>0;rep--)
{
int i;
for(i=0; i< 100000;i++)
{}
}
}

Hi,

The definition provided above is not crucial, as you can configure it directly in your code.

This configuration is specifically for the STM32F103C8 microcontroller, utilizing an 8 MHz external clock and setting the system frequency to 36 MHz. Please note that this information is based on my previous code, which I have copied here for reference.

void CLOCK(void){
    
    RCC_DeInit();     
    
    RCC_LSICmd(ENABLE);
    while(RCC_GetFlagStatus(RCC_FLAG_LSIRDY) == SET);
    
    RCC_HSEConfig(RCC_HSE_ON);
    
    while(RCC_WaitForHSEStartUp() != SUCCESS){}
        
            
    FLASH_PrefetchBufferCmd(FLASH_PrefetchBuffer_Enable);    
    FLASH_SetLatency(FLASH_Latency_2);    
    
        
    RCC_HCLKConfig(RCC_SYSCLK_Div1);    
    RCC_PCLK1Config(RCC_HCLK_Div2);                         
    RCC_PCLK2Config(RCC_HCLK_Div1);                        
        
    
        
    RCC_PLLCmd(DISABLE);
        
    RCC_PLLConfig(RCC_PLLSource_HSE_Div2,RCC_PLLMul_12);
                
    RCC_PLLCmd(ENABLE);
    
    while(RCC_GetFlagStatus( RCC_FLAG_PLLRDY)!=SET);
        
            
    RCC_SYSCLKConfig(RCC_SYSCLKSource_PLLCLK);
    
    while (RCC_GetSYSCLKSource() != 0x08){}
        
    FLASH_SetLatency(FLASH_Latency_1);    
    
}

As mentioned already:

Hans Schneebauer said:

Please remember that XTAL is a virtual register in the µVision simulator. It has no influence on your code and therefore your application

You need to define the clock-tree setup in your application. I suggest using STCube to do that. Please see our examples how to do that.