Imagecraft c compiler and development environment for the atmel avr

ICCV8 for AVR – C Compiler for Atmel AVRSince changing RAMPZ affects data SRAM access via the Z pointer registers, if youneed to modify RAMPZ, then you should save the previous value and restore it whenyou are done. We provide a set of library functions for accessing extended flashlocations that preserves the value of RAMPZ; see Greater Than 64K AccessFunctions for details.With the other RAMP registers, you can just safely use a register and set it to zeroafterward. This ensures that RAMP registers have the default values except in thecases where you need to modify them.Checking the AddressesTo check the address of a data or constant data, use View->”Map File” and search forthe symbol’s name. The addresses are in hexadecimal, so any address greater than64K bytes would have more than four hexadecimal digits.Using Library FunctionsWe provide a set of library functions to access flash and SRAM beyond the 64K byteboundary and preserve the values of any RAMP registers they use. See Greater Than64K Access Functions. While using library functions is less straightforward than if thecompiler directly supports mixed word and long addresses, in terms of code efficiency,there should not be any meaningful differences. (Nevertheless, we are investigatingthe feasibility of supporting mixed-size addresses, and will support the feature in alater update if possible.)Managing Constant DataThe compiler puts constant data (e.g. initialized global data that is qualified with the__flash keyword) in the .lit area, and the linker is set up to allocate space for allthe literal areas before the code area. Therefore, in most cases, unless you have a lotof constant data, it should all fit in the lower 64K byte flash memory space. In the casethat you do have more than 64K of constant data, the simplest approach is to identifysome data that you want to allocate to the upper 64K bytes, and then allocate it to itsown area:#pragma lit:upper64K_lit__flash int atable[] = { ....#pragma lit:litIn the Project->Options->Target, add-bupper64K_lit:0x?????128