Undefined constants

@Rolf:
Hi Rolf, we discussed that subject long ago in the topic "Updating Bootloader via Flash-Write" - and I used the means and possibilities you provided in the compiler. I know that section of the handbook, it is well marked in my old manual dating from 2007. Well, the example code is still there for download.
I attach a little memory map here that explains the design. A sketch can explain better than many words.
That design is based completely on your ideas, handbook and compiler, the only thing I changed, is the memory position of the flash write section for re-writing the bootloader. Since the crucial part requires only about 230 Bytes, I did not want to waste the rest of the unused boot area, so I placed it almost into the middle of the boot area, thus leaving almost 4 K boot area for the main application. (I was very short of memory in that project)

@Harald_K: A nice alternative to FlashPtr, I will try it. Thanks!

PS: The sketch is for a 128 K ATMega

ok, so lets do it this way:

1. you declare a normal const at the desired address:

const
CPULoaderVersion[$3FFFA] : word = $1234;

and put the statement

w := CPULoaderVersion;

in your code where you need it.

then you compile your project

from the IDE, use Datei / Öffnen / and select the .asm-File the Compiler has generated.

then scroll to the lines the compiler has produced for your w := ... statement,
mark them
copy them to the clipboard

switch back to your pascal source (at the line containing the w := .. statement

insert the text from the clipboard

put the asm; endasm; around it

prefix the const-declaration by //

replace the symbolic addresses of your constant by the physical adress in the RAMPZ / Z - statements.


so the compiler has done everything for you, selects the appropriate RAMPZ / Z / (E)LPM for your AVR etc.