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How is flash memory used in a C program?
This article talks about specifics of the C language implementation using GCC with the ARM Cortex-M architecture. Other implementations differ on specifics, but the basic concepts are the same. Code and read-only data are stored in flash memory. The layout of a C program’s flash memory is shown in the diagram above.
How much program memory does a PIC have?
Overview. The PIC has a relatively large amount of flash program memory (32 Kbytes) but relatively little data memory (1536 bytes of SRAM), as well as a very small amount of EEPROM (256 bytes). For some applications, we want to have lookup tables or calibration data stored on our PIC, but we don’t want it hogging data memory.
How to store data in Flash using arm compiler?
Plus require 64, 128, or 256 bytes of ram (or more) depending on the flash page size. Believe it or not, this page is the best thing that pops up when looking how to store data in flash with the AVR ARM compiler. “Static and global objects declared const are allocated in ROM.”
Can a C compiler generate a flash routine?
The C language, compilers, etc are not able to generate chip/board specific flash routines. If you wish to use flash pages to store read/write data you are going to have to have at least a page worth of ram and some read/write routines.
How is read only data stored in flash memory?
The read-only data section follows the text section and is exclusively stored in flash memory (note this is only true for some embedded architectures, not all). There is then a copy of the “data” section which contains the initial values of statically allocated variables. This section is copied to RAM when the program starts up.
How to optimize code and RAM size in Eclipse?
For a simple blinky, that is rather not small. The first thing is to check what the program is doing. The main.c has this: Basically the code is initializing the pins, clocks, sets up the SysTick timer and then does the ‘blinky’ in a loop, using the Systick counter to delay the blink period.
Which is the best way to optimize code size?
The best option for code size optimization is -Os (optimize for size): That looks now pretty reasonable! Of course there are now ways to cut off more for a ‘bare-bare-blinky’, but everything in place (startup code, clock and GPIO initialization) makes sense for a real application, so I stop here now. What does not look right is the SRAM usage.