Can You explain me something. Why in ARM microcontrollers each IDE use startup files? Where from the compiler knows that the first think is to execude the code from startup. Each C language programms should start from main() funcion and here the program starts from startup? If the startup does not exists it works fine too but we have to make Heap, stack and other by ourself but in main()? If I add different startup called whatever i want and add it to group in project in will be done the as first too so it means that the name of the startupp file is not important.
Can you explain me how does it work? (for example in Keil)
But how is it happen, for example in Keil, that the linker know (or compiller) that before main() it sholuld execute the code contained in startup file although the file can have different name? In other words what makes that the startup file is execute first?
In other words what makes that the startup file is execute firs
The location (mostly, in flash) of its binary image!
As I mentioned, there is a linker configuration file telling the linker how to order things.
It may look like:
; ************************************************************* ; *** Scatter-Loading Description File generated by uVision *** ; ************************************************************* LR_IROM1 0x00000000 0x00001000 { ; load region size_region ER_IROM1 0x00000000 0x00001000 { ; load address = execution address *.o (RESET, +First) *(InRoot$$Sections) .ANY (+RO) } RW_IRAM1 0x40000000 0x00008000 { ; RW data .ANY (+RW +ZI) } RW_IRAM2 0x7FE00000 0x00004000 { adc.o (+ZI) fram.o (+ZI) .ANY (+RW +ZI) } } LR_IROM2 0x00003000 0x0003D000 { ER_IROM2 0x00003000 0x0003D000 { ; load address = execution address .ANY (+RO) } }
Notice the "(RESET, +First)" part?
Match that up with the line in the startup assembler file:
AREA RESET, CODE, READONLY
So it doesn't matter what the startup file is named - if it contains an area "RESET" it will match the region placement of the linker configuration file.
But you can use the IDE to specify segment namings for C files too, and add other sorting orders in the linker configuration (scatter) file.
All that is required, is that you have a suitable startup code located where the physical processor initially jumps or reads a reset vector.
You want to say that is in some way independent. Startup is compiled its code is put in flash according to the given location and beside it jumps to main() function? I think I have missed something
Per reply explains it all. The common reference in the startup file and the scatter file to RESET places the startup at the entry address to internal flash.