IAR Simulator

I typically use Keil, not IAR. You could review the documentation, or speak to IAR Support staff.

I'd expect you need to check that box, and the one for TIM3, and also write code as you would on real hardware, otherwise there seems little point in having a 'simulator'. The simulator needs to reflect exactly what real hardware would do.

What would work on real hardware

// STM32 TIM3 1KHz (1ms) Update STM32F0-Discovery - sourcer32@gmail.com
#include 'stm32f0_discovery.h'
//**************************************************************************************
void TIM3_Config(void)
{
 TIM_TimeBaseInitTypeDef TIM_TimeBaseStructure;
 /* TIM3 Periph clock enable */
 RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM3, ENABLE);
 /* TIM3 Configuration */
 TIM_DeInit(TIM3);
 /* Time base configuration */
 TIM_TimeBaseStructInit(&TIM_TimeBaseStructure);
 TIM_TimeBaseStructure.TIM_Prescaler = 0;
 TIM_TimeBaseStructure.TIM_Period = (SystemCoreClock / 1000) - 1; // 1 KHz, from 48 MHz
 TIM_TimeBaseStructure.TIM_ClockDivision = 0;
 TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up;
 TIM_TimeBaseInit(TIM3, &TIM_TimeBaseStructure);
 /* TIM1 enable counter */
 TIM_Cmd(TIM3, ENABLE);
 /* Enable the Update Interrupt Request */
 TIM_ITConfig(TIM3, TIM_IT_Update, ENABLE);
}
//**************************************************************************************
void TIM3_IRQHandler(void)
{
 if (TIM_GetITStatus(TIM3, TIM_IT_Update) != RESET)
 {
 /* Clear TIM3_UPDATE interrupt pending bit */
 TIM_ClearITPendingBit(TIM3, TIM_IT_Update);
 // ..
 }
}
//**************************************************************************************
void NVIC_Config(void)
{
 NVIC_InitTypeDef NVIC_InitStructure;
 /* Enable and set TIM3 Interrupt */
 NVIC_InitStructure.NVIC_IRQChannel = TIM3_IRQn;
 NVIC_InitStructure.NVIC_IRQChannelPriority = 0;
 NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;
 NVIC_Init(&NVIC_InitStructure);
}
//**************************************************************************************
int main(void)
{
 NVIC_Config();
 TIM3_Config();
 while(1); /* Infinite loop */
}
//**************************************************************************************
#ifdef USE_FULL_ASSERT
/**
 * @brief Reports the name of the source file and the source line number
 * where the assert_param error has occurred.
 * @param file: pointer to the source file name
 * @param line: assert_param error line source number
 * @retval None
 */
void assert_failed(uint8_t* file, uint32_t line)
{
 /* User can add his own implementation to report the file name and line number,
 ex: printf('Wrong parameters value: file %s on line %d

', file, line) */
 /* Infinite loop */
 while (1)
 {
 }
}
#endif
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I'm sure IAR has some supporting documentation for the simulator, I'm not here to argue its function or usability, I'm sure it is not a gate-level / clock accurate model.