Diff: targets/cmsis/TARGET_NXP/TARGET_LPC11CXX/cmsis_nvic.c

Revision:

20:4263a77256ae

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/targets/cmsis/TARGET_NXP/TARGET_LPC11CXX/cmsis_nvic.c	Tue Sep 10 15:14:19 2013 +0300
@@ -0,0 +1,57 @@
+/* mbed Microcontroller Library - cmsis_nvic for LPC11U24
+ * Copyright (c) 2011 ARM Limited. All rights reserved.
+ *
+ * CMSIS-style functionality to support dynamic vectors
+ */ 
+
+#include "cmsis_nvic.h"
+
+/* In the M0, there is no VTOR. In the LPC range such as the LPC11U,
+ * whilst the vector table may only be something like 48 entries (192 bytes, 0xC0), 
+ * the SYSMEMREMAP register actually remaps the memory from 0x10000000-0x100001FF 
+ * to adress 0x0-0x1FF. In this case, RAM can be addressed at both 0x10000000 and 0x0
+ * 
+ * If we just copy the vectors to RAM and switch the SYSMEMMAP, any accesses to FLASH
+ * above the vector table before 0x200 will actually go to RAM. So we need to provide 
+ * a solution where the compiler gets the right results based on the memory map
+ *
+ * Option 1 - We allocate and copy 0x200 of RAM rather than just the table
+ *  - const data and instructions before 0x200 will be copied to and fetched/exec from RAM
+ *  - RAM overhead: 0x200 - 0xC0 = 320 bytes, FLASH overhead: 0
+ * 
+ * Option 2 - We pad the flash to 0x200 to ensure the compiler doesn't allocate anything there  
+ *  - No flash accesses will go to ram, as there will be nothing there
+ *  - RAM only needs to be allocated for the vectors, as all other ram addresses are normal
+ *  - RAM overhead: 0, FLASH overhead: 320 bytes
+ *
+ * Option 2 is the one to go for, as RAM is the most valuable resource
+ */
+
+#define NVIC_RAM_VECTOR_ADDRESS (0x10000000)  // Vectors positioned at start of RAM
+
+void NVIC_SetVector(IRQn_Type IRQn, uint32_t vector) {
+    int i;
+    // Space for dynamic vectors, initialised to allocate in R/W
+    static volatile uint32_t* vectors = (uint32_t*)NVIC_RAM_VECTOR_ADDRESS;
+
+    // Copy and switch to dynamic vectors if first time called
+    if((LPC_SYSCON->SYSMEMREMAP & 0x3) != 0x1) {     
+      uint32_t *old_vectors = (uint32_t *)0;         // FLASH vectors are at 0x0
+      for(i = 0; i < NVIC_NUM_VECTORS; i++) {    
+            vectors[i] = old_vectors[i];
+        }
+        LPC_SYSCON->SYSMEMREMAP = 0x1; // Remaps 0x0-0x1FF FLASH block to RAM block
+    }
+
+    // Set the vector 
+    vectors[IRQn + 16] = vector; 
+}
+
+uint32_t NVIC_GetVector(IRQn_Type IRQn) {
+    // We can always read vectors at 0x0, as the addresses are remapped
+    uint32_t *vectors = (uint32_t*)0; 
+
+    // Return the vector
+    return vectors[IRQn + 16];
+}
+