stm_systick.csr = ((1 << STM_SYSTICK_CSR_ENABLE) |
(1 << STM_SYSTICK_CSR_TICKINT) |
(STM_SYSTICK_CSR_CLKSOURCE_HCLK_8 << STM_SYSTICK_CSR_CLKSOURCE));
stm_systick.csr = ((1 << STM_SYSTICK_CSR_ENABLE) |
(1 << STM_SYSTICK_CSR_TICKINT) |
(STM_SYSTICK_CSR_CLKSOURCE_HCLK_8 << STM_SYSTICK_CSR_CLKSOURCE));