Lpc2000

ebarker123 wrote:

>Thanks for you excellent reply. Is this for the GNU compiler ?
>I failed to mention that I'm using the Keil compiler.
>I've determined that the following directives do the trick.
>
>#pragma NOINIT
>char states[100];     /* Uninitialized Variable */
>
>#pragma INIT
>char array[100];      /* Initialized Variable */
>
>  
>
Well, that would work with Kiel, I guess.  I don't use a Keil dev 
system, my system is GNU compiled from source.  YMMV.

TomW


>Ed
>
>
>--- In lpc2000@yahoogroups.com, Tom Walsh <tom@...> wrote:
>  
>
>>ebarker123 wrote:
>>
>>    
>>
>>>Here is the scenario.
>>>
>>>I have an MCB2138 eval board. I have a menu talking on a serial port.
>>>
>>>Using the menu, I can set and print a variable called 'mytemp'.
>>>
>>>I set the value to say, 456, and print that out.
>>>
>>>I press reset and the value is changed to 0. 
>>>Where/How is this variable getting changed. My application requires
>>>that we be able to press reset, and the SRAM contents not change.
>>>
>>> 
>>>
>>>      
>>>
>>Look in your crt0.s file, bss sections are zeroed there.  'bss' data is 
>>data which you declared globally and did not provide a value for. 
>>    
>>
>*ALL* 
>  
>
>>C code systems initialize the bss data section, all, this is a 
>>requirement of the C language.
>>
>>If you want to create memory which is part of the code but is not 
>>initialized, add a section attribute to it and then place the section 
>>into the linker ld script.  For example:
>>
>>char myString [8] __attribute__((section ("noinit")));
>>
>>in the linker script, place a new section AFTER the bss.  You want to 
>>avoid placing this in front of "__bss_end__ = . ;"!
>>
>>================= begin LPC2106ROM.ld ===============
>>  /* .bss section which is used for uninitialized data */
>>  .bss (NOLOAD) :
>>  {
>>    __bss_start = . ;
>>    __bss_start__ = . ;
>>    *(.bss)
>>    *(COMMON)
>>    . = ALIGN(4);
>>  } > RAM
>>
>>  . = ALIGN(4);
>>  __bss_end__ = . ;
>>  PROVIDE (__bss_end = .);
>>
>>   .myvars (NOLOAD) :
>>   {
>>    *(noinit)
>>   } > RAM
>>
>>  .stack ALIGN(256) :
>>  {
>>    . += STACK_SIZE;
>>    PROVIDE (_stack = .);
>>  } > RAM
>>
>>  _end = . ;
>>  PROVIDE (end = .);
>>
>>================== snip ====================
>>
>>Note the new region called ".myvars" in the script?  That is where I 
>>will put the "noinit" section.
>>
>>To make sure that all is well, look at the symbol file produced by the 
>>linker.  In my case it is main2106.sym, in it I look at the memory 
>>location of '__bss_end__' and 'myString'.  Here is a snippet of my 
>>symbols file:
>>
>>============= begin main2106.sym ===============
>>400092e2 B serial1ParityMode
>>400092e4 B tx1Buffer
>>40009ae8 B Words
>>40009dec B WordCnt
>>40009df0 A __bss_end__
>>40009df0 B myString
>>4000ae00 A end
>>4000ae00 A _end
>>4000ae00 B _stack
>>
>>================= snip =====================
>>
>>Actually, that is the very end of the symbol file.  The variable 
>>myString is placed at the end of the RAM.   Adding more data to this
>>    
>>
>new 
>  
>
>>section is quite easy now, simply assign the same attribute to each:
>>
>>char myString [8] __attribute__((section ("noinit")));
>>
>>struct BIG_DATA abort_info  __attribute__((section ("noinit")));
>>
>>int timeAborted __attribute__((section ("noinit")));
>>
>>...
>>
>>Hope this helps,
>>
>>TomW
>>
>>
>>
>>
>>-- 
>>Tom Walsh - WN3L - Embedded Systems Consultant
>>http://openhardware.net, http://cyberiansoftware.com
>>"Windows? No thanks, I have work to do..."
>>----------------------------------------------------
>>
>>    
>>
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-- 
Tom Walsh - WN3L - Embedded Systems Consultant
http://openhardware.net, http://cyberiansoftware.com
"Windows? No thanks, I have work to do..."
----------------------------------------------------