System timer[SysTick timer details for STM32]

 Interrupt with divided 9 MHz system clock as SysTick timer：  ①　Set counter value for SysTick timer　  ②　Specify system clock source The argument can be either the AHB clock as it is or a clock divided by 8. ■　SysTick_CLKSource_HCLK : AHB clock as is■　SysTick_CLKSource_HCLK_Div8 : AHB clock divided by 8  ③　Description of Interrupt Processing