- #How to declare rom variable in keil mdk arm update
- #How to declare rom variable in keil mdk arm code
These values need to be placed into non-volatile memory, which can be read-only (e.g. a peripheral register address or a hard-coded delay time.
#How to declare rom variable in keil mdk arm code
Running code from RAM can also be used to construct self-modifying software, but that is a rather exotic use-case.
#How to declare rom variable in keil mdk arm update
This is mainly useful in order to run the code faster (since FLASH is rather slow to access) or in order to implement some update functionality that can update the whole FLASH memory. Modern MCU's usually read their instructions from FLASH but can also execute code from RAM. From a programmers point of view we want to differentiate between Code (Instructions) and Data.Ĭode is usually stored in some kind of non-volatile memory (ROM, FLASH, etc.) and is read and executed at runtime by the processor core. Let's try to break this down in a systematic way. Of course I know, that flash is Read-only and that SRAM is read-write but then there is code memory and data memory on IAR's side, and ZI-data and Code on Keil's side.Īnyone here who has more in depth knowledge about this? Unfortunately, I am not quite sure how IAR and Keil measure code size.įor example, IAR gives me this output: 868 bytes of readonly code memoryĪnd Keil this: Program Size: Code=676 RO-data=252 RW-data=0 ZI-data=1640Īt a first glance I am not able to detect which amount of bytes relates to used flash size and which to used SRAM. Because of that, I found it interesting to compare both compilers regarding code size (which is the most critical for small microcontrollers).īoth compilers were set on max. It is advised to enable the generation of this as indicated in Figure 11.I am currently developing a small project for an STM32F103 microcontroller which features a Cortex-M3 CPU.ĭue to CMSIS standard header files it is possible to use the exact same code with IAR and Keil µVision.
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During initialization code and data will be copied, if necessary, from Before the code reaches int main(void) in arch_main.c, the initialization code is executed. A Load Region instructs the linker where to place code and data and the initialization code for It is comprised of Load Region descriptors and Execution Region descriptors.