Atmel provided hardware specifics.

Demo/Common/drivers/Atmel/at91lib/boards/at91sam9xe-ek/board_lowlevel.c

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+/* ----------------------------------------------------------------------------
+ *         ATMEL Microcontroller Software Support 
+ * ----------------------------------------------------------------------------
+ * Copyright (c) 2008, Atmel Corporation
+ *
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * - Redistributions of source code must retain the above copyright notice,
+ * this list of conditions and the disclaimer below.
+ *
+ * Atmel's name may not be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * DISCLAIMER: THIS SOFTWARE IS PROVIDED BY ATMEL "AS IS" AND ANY EXPRESS OR
+ * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT ARE
+ * DISCLAIMED. IN NO EVENT SHALL ATMEL BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA,
+ * OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
+ * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
+ * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE,
+ * EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ * ----------------------------------------------------------------------------
+ */
+
+//------------------------------------------------------------------------------
+//         Headers
+//------------------------------------------------------------------------------
+
+#include "board.h"
+#include "board_memories.h"
+
+//------------------------------------------------------------------------------
+//         Local definitions
+//------------------------------------------------------------------------------
+
+//------------------------------------------------------------------------------
+/// \page "SAM9XE - Oscillator & PLL Parameters"
+/// This page lists the parameters which are set for the PLL and main
+/// oscillator configuration.
+///
+/// !Parameters
+/// - BOARD_OSCOUNT
+/// - BOARD_CKGR_PLLA
+/// - BOARD_PLLACOUNT
+/// - BOARD_MULA
+/// - BOARD_DIVA
+/// - BOARD_CKGR_PLLB
+/// - BOARD_PLLBCOUNT
+/// - BOARD_MULB
+/// - BOARD_DIVB
+/// - BOARD_USBDIV
+/// - BOARD_PRESCALER
+
+/// Main oscillator startup time (in number of slow clock ticks). 
+#define BOARD_OSCOUNT           (AT91C_CKGR_OSCOUNT & (64 << 8))
+
+/// PLLA frequency range.
+#define BOARD_CKGR_PLLA         (AT91C_CKGR_SRCA | AT91C_CKGR_OUTA_2)
+/// PLLA startup time (in number of slow clock ticks).
+#define BOARD_PLLACOUNT         (63 << 8)
+/// PLLA MUL value.
+#define BOARD_MULA              (AT91C_CKGR_MULA & (96 << 16))
+/// PLLA DIV value.
+#define BOARD_DIVA              (AT91C_CKGR_DIVA & 9)
+
+/// PLLB frequency range
+#define BOARD_CKGR_PLLB         AT91C_CKGR_OUTB_1
+/// PLLB startup time (in number of slow clock ticks).
+#define BOARD_PLLBCOUNT         BOARD_PLLACOUNT
+/// PLLB MUL value.
+#define BOARD_MULB              (124 << 16)
+/// PLLB DIV value.
+#define BOARD_DIVB              12
+
+/// USB PLL divisor value to obtain a 48MHz clock.
+#define BOARD_USBDIV            AT91C_CKGR_USBDIV_2
+/// Master clock prescaler value.
+#define BOARD_PRESCALER         AT91C_PMC_MDIV_2
+//------------------------------------------------------------------------------
+
+//------------------------------------------------------------------------------
+//         Local functions
+//------------------------------------------------------------------------------
+
+//------------------------------------------------------------------------------
+/// Default spurious interrupt handler
+//------------------------------------------------------------------------------
+void DefaultSpuriousHandler(void)
+{
+    while (1);
+}
+
+//------------------------------------------------------------------------------
+/// Default handler for fast interrupt requests.
+//------------------------------------------------------------------------------
+void DefaultFiqHandler(void)
+{
+    while (1);
+}
+
+//------------------------------------------------------------------------------
+/// Default handler for standard interrupt requests.
+//------------------------------------------------------------------------------
+void DefaultIrqHandler(void)
+{
+    while (1);
+}
+
+//------------------------------------------------------------------------------
+//         Global functions
+//------------------------------------------------------------------------------
+
+//------------------------------------------------------------------------------
+/// Performs the low-level initialization of the chip.
+//------------------------------------------------------------------------------
+void LowLevelInit(void)
+{
+    unsigned char i;
+
+    // Set flash wait states
+    //----------------------
+    AT91C_BASE_EFC->EFC_FMR = 6 << 8;
+
+//#if !defined(sdram)
+    // Initialize main oscillator
+    //---------------------------
+    AT91C_BASE_PMC->PMC_MOR = BOARD_OSCOUNT | AT91C_CKGR_MOSCEN;
+    while (!(AT91C_BASE_PMC->PMC_SR & AT91C_PMC_MOSCS));
+
+    // Initialize PLLA at 200MHz (198.656)
+    AT91C_BASE_PMC->PMC_PLLAR = BOARD_CKGR_PLLA
+                                | BOARD_PLLACOUNT
+                                | BOARD_MULA
+                                | BOARD_DIVA;
+    while (!(AT91C_BASE_PMC->PMC_SR & AT91C_PMC_LOCKA));
+
+    // Initialize PLLB for USB usage
+    AT91C_BASE_PMC->PMC_PLLBR = BOARD_USBDIV
+                                | BOARD_CKGR_PLLB
+                                | BOARD_PLLBCOUNT
+                                | BOARD_MULB
+                                | BOARD_DIVB;
+    while (!(AT91C_BASE_PMC->PMC_SR & AT91C_PMC_LOCKB));
+
+    // Wait for the master clock if it was already initialized
+    while (!(AT91C_BASE_PMC->PMC_SR & AT91C_PMC_MCKRDY));
+
+    // Switch to fast clock
+    //---------------------
+    // Switch to main oscillator + prescaler
+    AT91C_BASE_PMC->PMC_MCKR = BOARD_PRESCALER;
+    while (!(AT91C_BASE_PMC->PMC_SR & AT91C_PMC_MCKRDY));
+
+    // Switch to PLL + prescaler
+    AT91C_BASE_PMC->PMC_MCKR |= AT91C_PMC_CSS_PLLA_CLK;
+    while (!(AT91C_BASE_PMC->PMC_SR & AT91C_PMC_MCKRDY));
+//#endif //#if !defined(sdram)
+
+    // Initialize AIC
+    //---------------
+    AT91C_BASE_AIC->AIC_IDCR = 0xFFFFFFFF;
+    AT91C_BASE_AIC->AIC_SVR[0] = (unsigned int) DefaultFiqHandler;
+    for (i = 1; i < 31; i++) {
+
+        AT91C_BASE_AIC->AIC_SVR[i] = (unsigned int) DefaultIrqHandler;
+    }
+    AT91C_BASE_AIC->AIC_SPU = (unsigned int) DefaultSpuriousHandler;
+
+    // Unstack nested interrupts
+    for (i = 0; i < 8 ; i++) {
+
+        AT91C_BASE_AIC->AIC_EOICR = 0;
+    }
+
+    // Watchdog initialization
+    //------------------------
+    AT91C_BASE_WDTC->WDTC_WDMR = AT91C_WDTC_WDDIS;
+
+    // Remap
+    //------
+    BOARD_RemapRam();
+
+    // Disable RTT and PIT interrupts (potential problem when program A
+    // configures RTT, then program B wants to use PIT only, interrupts
+    // from the RTT will still occur since they both use AT91C_ID_SYS)
+    AT91C_BASE_RTTC->RTTC_RTMR &= ~(AT91C_RTTC_ALMIEN | AT91C_RTTC_RTTINCIEN);
+    AT91C_BASE_PITC->PITC_PIMR &= ~AT91C_PITC_PITIEN;
+}
+