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git-svn-id: https://src.develer.com/svnoss/bertos/trunk@4376 38d2e660-2303-0410-9eaa-f027e97ec537

diff --git a/bertos/algo/crc.c b/bertos/algo/crc.c
index c7444740144b4c77f14bd42079552ac6a83e2270..d4293f9e063e82d4b7a90359d80a76f928b12eeb 100644 (file)
--- a/bertos/algo/crc.c
+++ b/bertos/algo/crc.c
@@ -38,8 +38,14 @@
 
 #include "crc.h"
 
-/**
- * crctab calculated by Mark G. Mendel, Network Systems Corporation
+/*
+ * The boot on AVR cpu is placed at the end of flash memory, but the avr
+ * address memory by byte and the pointers are 16bits long, so we are able
+ * to address 64Kbyte memory max. For this reason we can't read the crctab
+ * from flash, because it is placed at the end of memory. This is true every
+ * time we have an AVR cpu with more that 64Kbyte of flash. To fix this problem
+ * we let the compiler copy the table in RAM at startup. Obviously this solution
+ * is not efficent, but for now this is the only way.
  */
 #if CPU_HARVARD && !(defined(ARCH_BOOT) && (ARCH & ARCH_BOOT))
        #define CRC_TABLE const uint16_t PROGMEM crc16tab[256]
@@ -47,6 +53,9 @@
        #define CRC_TABLE const uint16_t crc16tab[256]
 #endif
 
+/**
+ * crctab calculated by Mark G. Mendel, Network Systems Corporation
+ */
 CRC_TABLE = {
        0x0000, 0x1021, 0x2042, 0x3063, 0x4084, 0x50a5, 0x60c6, 0x70e7,
        0x8108, 0x9129, 0xa14a, 0xb16b, 0xc18c, 0xd1ad, 0xe1ce, 0xf1ef,