Hi Please, How i implement this code in CARM? ///////////////////////////////////////////// typedef struct _AT91S_RTC { AT91_REG RTC_CR; // Control Register AT91_REG RTC_MR; // Mode Register AT91_REG RTC_TIMR; // Time Register AT91_REG RTC_CALR; // Calendar Register AT91_REG RTC_TIMALR; // Time Alarm Register AT91_REG RTC_CALALR; // Calendar Alarm Register AT91_REG RTC_SR; // Status Register AT91_REG RTC_SCCR; // Status Clear Command Register AT91_REG RTC_IER; // Interrupt Enable Register AT91_REG RTC_IDR; // Interrupt Disable Register AT91_REG RTC_IMR; // Interrupt Mask Register AT91_REG RTC_VER; // Valid Entry Register } AT91S_RTC, *AT91PS_RTC; #define AT91C_BASE_MC ((AT91PS_MC) 0xFFFFFF00) // (MC) Base Address #define AT91C_BASE_RTC ((AT91PS_RTC) 0xFFFFFE00) // (RTC) Base Address ///////////////////////////////////////////// I need access SFR whit structures For example I tried this: ////////////////////////////////// typedef struct { at91_reg PS_CR; /* Control Register */ at91_reg PS_PCER ; /* Peripheral Clock Enable Register */ at91_reg PS_PCDR ; /* Peripheral Clock Disable Register */ at91_reg PS_PCSR ; /* Peripheral Clock Status Register */ }StructPS; StructPS *PS_BASE __at 0xFFFF4000; //////////////////////////// When i try change the PS_PCER value: PS_BASE->PS_PCER = 0x04; The 0xFFFF4004 (PS_PCER) value not is affected (I saw this in Simulator). What's wrong? can you help me? Thank's Eduardo