C语言 指向特定固定地址的指针
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Pointer to a specific fixed address
提问by Peter Luke
How do you assign a specific memory address to a pointer?
如何为指针分配特定的内存地址？
The Special Function Registers in a microcontroller such AVR m128 has fixed addresses, the AVR GCC defines the SFR in the io.h header file, but I want to handle it myself.
AVR m128 等微控制器中的特殊功能寄存器具有固定地址，AVR GCC 在 io.h 头文件中定义了 SFR，但我想自己处理。
回答by Carl Norum
Sure, no problem. You can just assign it directly to a variable:
好没问题。您可以直接将其分配给变量：
volatile unsigned int *myPointer = (volatile unsigned int *)0x12345678;
What I usually do is declare a memory-mapped I/O macro:
我通常做的是声明一个内存映射 I/O 宏：
#define mmio32(x) (*(volatile unsigned long *)(x))
And then define my registers in a header file:
然后在头文件中定义我的寄存器：
#define SFR_BASE (0xCF800000)
#define SFR_1 (SFR_BASE + 0x0004)
#define SFR_2 (SFR_BASE + 0x0010)
And then use them:
然后使用它们：
unsigned long registerValue = mmio32(SFR_1); // read
mmio32(SFR2) = 0x85748312; // write
