CM3 支持 64 位整数, LDRD STRD

1 ;CM3 在一定程度上支持 64 位整数。 2 ;其中 LDRD/STRD 就是为 64 位整数的数据传送而设的，语法 格式为： 3 4 LDRD.W RL, RH, [Rn, #+/-offset] {!} 5 STRD.W RL, RH, [Rn, #+/-offset] {!} 6 LDRD.W RL, RH, [Rn],#+/-offset 7 STRD.W RL, RH, [Rn],#+/-offset 8 9 LDR R2, =0x1000 ;(0x1000)= 0x1234_5678_ABCD_EF00 : 00 EF CD AB 78 56 34 12 10 LDRD.W R0, R1,[R2] ;R0= 0xABCD_EF00, R1=0x1234_5678 11 STRD.W R1, R0,[R2] ;(0x1000)=0xABCD_EF00_1234_5678 : 78 56 34 12 00 EF CD AB

Memory : [ RL ] [ RH ]

For example, the following piece of code stores the 64-bit value 0x0123456789ABCDEF to address 0xA0000000: void perip_64bitaccess(void) { unsigned long long value = 0x0123456789ABCDEF; *((volatile unsigned long long*) (0xA0000000)) = value; }

 

 

__asm void stm_llout(unsigned long long* addr, unsigned long long value) { STM r0, {r2,r3} BX LR } __asm unsigned long long ldm_llin(unsigned long long* addr) { LDM r0, {r0,r1} BX LR } unsigned long long perip_64bitaccess(void) { unsigned long long ullvalue = ldm_llin((unsigned long long*)0x40004000); stm_llout((unsigned long long*)0x40000000, ullvalue); return ullvalue; }

 

转载于:https://www.cnblogs.com/shangdawei/archive/2012/09/10/2678347.html

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