加密保护的机制Datasheet上都有详细说明。
具体特定芯片的加密，需仔细阅读datasheet中Flash spec及相关保护寄存器的spec，结合下面历程灵活更改（补充了datasheet的例程）。
在做访问保护操作之前，先将永久（临时）解访问保护程序烧入IFlash.
Set (XPEN, ROMEN) @ SYSCON register as “1”
Set XFLASHEN @XPERCON register as “1”
1)Write Protection, Enable Write Protection of sectors B0F4 of Bank 0 in I-Flash module.
FCR0H |= 0x0100; /* Set SPR in FCR0H*/
FARL = 0xDFB4; /*Load Add of register FNVWPIR in FARL*/
FARH = 0x000E; /*Load Add of register FNVWPIR in FARH*/
FDR0L = 0xFFEF; /*Load Data in FDR0L*/
FDR0H = 0xFFFF; /*Load Data in FDR0H*/
FCR0H |= 0x8000; /* Operation start*/
2)Temporary un-write protection, B0F4 temporarily un-write protection and programmingB0F4
FCR0H |=0x0100;
FARL = 0xDFB4;
FARH = 0x000E;
FDR0L = 0xFFFF; /*Load Data in FDR0L*/
FDR0H = 0xFFFF;
FCR0H |= 0x8000;
FCR0H |=0x2080; /* Set WPG & SMOD in FCR0H*/
FARL = 0x8000; /* Load B0F4 Add into FAR*/
FARH = 0x0001;
FDR0L = 0xAAAA; /* Load Data in FDR*/
FDR0H = 0xFFFF;
FCR0H |=0x8000; /* Operation start*/
3)Access Protection
Temp = FNVAPR0;
Temp &= 0xFFFC; /* Set DBGP, ACCP as “0” in FNVAPR0*/
FCR0H |= 0x0100; /* Set SPR in FCR0H */
FARL = 0xDFB8; /* Load Add of FNVAPR0 into FARL*/
FARH = 0x000E; /* Load Add of FNVAPR0 into FARH */
FDR0L = Temp; /* Load Data into FDR0L*/
FCR0H |= 0x8000; /* Operation start*/
Notes: 1) The Default value of FNVAPR0 is ACFF;
2) Set both DBGP and ACCP in FNVAPR0 as “0” to disable Access protection permanently.
4)Disable in a permanent way Access Protection
FCR0H |= 0x0100;
FARL = 0xDFBC; /* Load FNVAPR1 Add into FAR*/
FARH = 0x000E;
FDR0L = 0xFFFE; /* Load Data into FDR*/
FDR0H = 0xFFFF;
FCR0H |= 0x8000;
Notes: 1) Disable access protection routines must be programmed into I-Flash before Access protection operation
5) Enable in a permanent way Access Protection
FCR0H |= 0x0100;
FARL = 0xDFBC; /* Load FNVAPR1 Add into FAR*/
FARH = 0x000E;
FDR0L = 0xFFFE; /* Load Data into FDR*/
FDR0H = 0xFFFE;
FCR0H |= 0x8000;
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