ROM中的字符串常量怎么添加

试试这个：



      以下为原文

    Try this:

const char PROJECT[] @ 0x100 = "SCRPCB1";
const char VERSION[] @ 0x110 = "1.10";

您可能需要在程序中使用它来阻止编译器优化它。



      以下为原文

    You may need to use it in the program to stop the compiler from optimizing it away.

如果它被优化了，添加这个：或者使它们挥发。



      以下为原文

    If it is being optimized away, add this:

#asm
global _PROJECT ; so it won't get optimized out for non-used
global _VERSION
#endasm

or make them volatile.

@addr结构似乎工作得很好，比_u._方法更简洁一些。我认为“volatile”只适用于RAM变量，而不适用于ROM常量。从给定位置开始，以下似乎是顺序分配几个常量的好方法：谢谢你的建议。



      以下为原文

    The @addr construct seems to work well, and is a bit cleaner than the __attribute__ method.
 
I think "volatile" applies only to RAM variables and not ROM constants.
 
The following seems to be a good way to assign several constants sequentially, starting at a given location:
 
__attribute__((address(0x110)))    const char VERSION[] = "1.10", DATE[] = "07/09/2016";
Thanks for the ideas.

const限定对象不是“常量”，而是“只读”。const volatile的示例用法来自http://publications.gbdir...onst_and_volatile.html。



      以下为原文

   
A const qualified object is not "constant" but is "read-only".
 
An example usage of const volatile is from http://publications.gbdir...onst_and_volatile.html .
 
Here's an article discussing Combining C's volatile and const Keywords.

那些是很好的参考资料。它仍然有点混乱，但它是有道理的。一个问题是，Windows环境和PIC微控制器之间的硬件差别，在Windows环境中，一切都从磁盘存储转移到RAM，PIC微控制器具有独特的RAM、ROM和EEPROM内存空间以及SFR。似乎C18编译器（大约从2005年开始我几乎只使用它）和XC8有了一些重大的改变，我已经使用了几年。我之前的大多数项目，特别是那些没有使用PIC18处理器的项目，都是在组装中。这两个编译器之间的内存映射已经发生了很大的变化，而且我认为在每个编译器或汇编器中，还有很多用于变量和常量声明的可选方法，链接器。似乎在XC8中不再认可“ROM”或“ROMDATA”限定符。对于C18、PICC18、XC8和XC16等，也可能存在一些差异。以下是MPLABX帮助中的一些示例：示例：在Data MemoryPICC18#pragma psect oldbss=mybss int gi；C18#pragma udata mybss int gi；XC16 int_.(u.("mybss"))gi的用户部分中指定未初始化变量，其中oldbss是psect(.)的名称；示例：将变量Mabonga定位在地址0x100的Data MemoryPICC18 int Mabonga@0x100；C18#pragma idata myDataSection=0x100；int Mabonga=1；XC16 int_.((address(0x100))Mabonga=1；示例：指定要放置在程序Mem中的变量ORyPICC18constcharmy_const_const_my_const_const_char_my_const_const_.[10]={0,1,1,2,2,3,3,3,3,3,3,3,3,3,3,3,3,3,4,5,6,7,8,8,9}；XC16常数或_u.u._my_const my_const my_const_((空间(auto_psv))char my_const my_const(空间)char my_const(空间(auto(auto_psv)))char my_const)char my_const_const_const_const(空间(空间(auto(auto(auto_psv)))char 5,6,7,8,9}；示例：在Add处找到函数PrintString在程序MemoryPICC18 int PrintString(const char*s)@0x8000{...}C18#pragma代码myTextSection=0x8000;int PrintString(const char*s){...}XC16 int_.((address(0x8000))PrintString(const char s){...}示例编译器自动保存和恢复变量变量1和var2PICC18没有等价的C18#pragma中断isr0 save=var1，var2 void isr0(void){/*执行中断函数here*/}XC16 void_.(u inter._(u save_var1,var2))isr0(void){/*执行中断函数here*/}



      以下为原文

    Those are some excellent references. It is still a bit confusing, but it makes sense. One issue is the difference in hardware between something like a Windows environment, where everything is transferred from disc storage to RAM, and a PIC microcontroller, which has distinct RAM, ROM, and EEPROM memory spaces, as well as SFRs. It also seems that there have been some major changes from the C18 compiler (which I had used almost exclusively since about 2005), and the XC8, which I have been using for a few years. Most of my earlier projects, particularly those not using the PIC18 processors, were in assembly.
 
The memory mapping has changed considerably between the two compilers, and I think there are also quite a few alternate methods for variable and constant declarations within each compiler or assembler, and linker. It seems that the "rom" or "romdata" qualifiers are no longer recognized in XC8. There are also some differences for C18, PICC18, XC8, and XC16, among others, perhaps. Here are some examples from the MPLABX Help:
 

Example: Specify an Uninitialized Variable in a User Section
in Data Memory
 PICC18
#pragma psect oldbss=mybss
int gi;
C18
#pragma udata mybss
int gi;
XC16
int __attribute__((__section__(".mybss"))) gi;
 
where oldbss is the name of the psect (section) in which the variable would normally be placed.
Example: Locate the Variable Mabonga at Address 0x100 in Data Memory
 PICC18
int Mabonga @ 0x100;
C18
#pragma idata myDataSection=0x100;
int Mabonga = 1;
XC16
int __attribute__((address(0x100))) Mabonga = 1;
 
Example: Specify a Variable to be Placed in Program Memory
 PICC18
const char my_const_array[10] = {0,1,2,3,4,5,6,7,8,9};
C18
#pragma romdata const_table
const rom char my_const_array[10] =
{0,1,2,3,4,5,6,7,8,9};
XC16
const or
__ attribute__((space(auto_psv)))
char my_const_array[10] = {0,1,2,3,4,5,6,7,8,9};
 
 
Example: Locate the function PrintString at Address 0x8000 in Program Memory
 PICC18
int PrintString(const char *s)@ 0x8000 {...}
C18
#pragma code myTextSection=0x8000;
int PrintString(const char *s){...}
XC16
int __attribute__((address(0x8000))) PrintString
(const char *s) {...}
 
Example: Compiler automatically SaveS and Restores the Variables var1 and var2
 PICC18
No equivalent
C18
#pragma interrupt isr0 save=var1, var2
void isr0(void)
{
/* perform interrupt function here */
}
XC16
void __attribute__((__interrupt__(__save__(var1,var2))))
isr0(void)
{
/* perform interrupt function here */
}