Not only floating point operations have numerical problems, but they can also lead to performance problems as in the following (simplified) example: #define NOF 64įsamples = samples*3.3/4096.0 - fZeroCurrent ĪRM designed the Cortex-M4 architecture in a way it is possible to have an FPU added. These includes clustering all variables that are initialized with the value zero (zero-initialization) and providing different data compression methods for non-zero initialized variables.My mantra is *not* to use any floating point data types in embedded applications, or at least to avoid them whenever possible: for most applications, they are not necessary and can be replaced by fixed point operations. Since a typical program requires quite a lot of those initialization values, modern compilers implement different optimization methods to reduce the memory footprint of this initializers. This initial value is actually nothing else than a constant data value (see above), that is automatically copied to its associated variable at the beginning of its lifetime. the starting value of a loop count variable).
#Iar arm cortex m code
Running code from RAM can also be used to construct self-modifying software, but that is a rather exotic use-case.
#Iar arm cortex m 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. 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.