Maybe this is a simple question, but I just couldn't figure it out. Can someone tell me how to place a constant variable into the specific ROM area? I would like to be able to set a constant value at a particualr ROM area and use a pointer to get it whenever I need it. Cheers, Tang
unfortunately, the _at_ keyword can't be used with initialisation. How about
code const unsigned char fred = 0xaa;
How to use linker to fix the location?
Dunno - I'm afraid you'll have to look that up for yourself in the manuals (which are all in PDF format on the free CD, and can be accessed via the Books tab in the uVision Project window): Look in the C51 manual for where it describes C51's segment naming & usage conventions, then look in the Assembler/Utilities manual for how to locate a specific segment at a specific address. Or try searching the Keil knowledge base, http://www.keil.com/search.asp Or, as your E-Mail appears to be at the University of Warwick, can you just pop over and ask the very nice people at Hitex? ;-)
Ha.. :)) good suggestion. Hitex is a good source of knowledge.
Here is a link to the knowledgebase atricle that describes how to do this. http://www.keil.com/support/docs/301.htm Jon
Exactly what I am looking for. CHEERS!!
I still dream of this construct:
const unsigned char code magicNum _at_ 0x8000 = 0xAA;
and why ever not?
Thanks for that, Jon. As you can probably tell, I've done this before - but not yet with the Keil toolset. I'm sure it'll come in handy.
Mark, your dream has become true in C251 v2.14 already. I use it to store the Revision code of the application. Franc
Impossible! How could that be? How could C251 get that feature before C51? C51 is probably used 10 to 1 over C251. Unfare! I declare a 10 yard penalty, repeat second down (Man it's great to have the XFL now. February can be so cold without football). - Mark
Here is how I do it: 1. I define the code version in the header file:
/*********************** FIRMWARE CODE VERSION *****************************/ #define CODE_VERSION 3 // 10 is version 1.0
unsigned char code version _at_ 0x0006 = CODE_VERSION;
That's what I thought. I'm still dreaming of this feature for the C51. - Mark
Please see my latest posting re this issue. It differs slightly from your example. Specifically: User's guide, 01.97, C compiler C51 on page 63 'explicitly defined memory types' recommends a syntax. The Utilities guide, 04.95, page 119, has a different syntax in files c_mess0.c, c_mess1.c. the utilities guide contradicts the recommendation in the user's guide. Yet the 'preferred' method in the C51 compiler will NOT work. You must use the 'obsolete' method of the Utilities guide. (1) Please explain. (2) What is correct syntax for: const unsigned char code *MyArray[NumberFruits] = {"apple,"banana","cherry"};
this is a copy of my posting today. If I follow the recommendation of the compiler manual, the linker puts the table of pointers into xdata. I must use the non-preferred method (per the utilities manual). Thanks. By the way, I can't find the pdf for the utilites manual. Is there one? === paste === User's guide, 01.97, C compiler C51 on page 63 'explicitly defined memory types' recommends a syntax. The Utilities guide, 04.95, page 119, has a different syntax in files c_mess0.c, c_mess1.c. the utilities guide contradicts the recommendation in the user's guide. Yet the 'preferred' method in the C51 compiler will NOT work. You must use the 'obsolete' method of the Utilities guide. (1) Please explain. (2) What is correct syntax for: const unsigned char code *MyArray[NumberFruits] = {"apple,"banana","cherry"};