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Hi i have less experience in embedded systems and i am using lpc1788 micro With 2mb external memory on board. I could successfully use from external memory(I could successfully use from it in tft lcd). but I can not initialize keil to use from it as default heap location). has any one experience to use external memory as heap? can any one give step by step guide to me to do that? and secondly question : exist any problem for use 16 bit external memory in 32 bit microcontrollers? excuse me for my bad English. thanks for your attention.
hi thanks for your response. i read your suggested document and also when i exploring in internet,i could find a useful document about access external ram as heap(stackoverflow.com/.../how-can-i-access-to-external-memory-as-heap),i implement these instruction carefully but it did not work!! i think problem is that 32 bit processor can not use 16 bit * 2mb sdram for heap. perhaps it dose not correct,now i want know is it possible implement heap in 16 bit external ram?? thanks for your attention.
You have to configure the micro to use the external memory by programing/initializing it's external bus interface. This will require you to look at the documentation for the chips being used, and the specific configurations of your board. There should be examples/documentation showing you how to set up the memory.
In the CMSIS model you'd want to add that into the SystemInit() function prior to the C run time initializes it's memory space and calls your main() function.
There is no reason the memory cannot be used for all the normal applications, it will however be a bit slower to access.
Your post does not convey and specifics about the SRAM chips, schematic or board. You should contact the board designers for support of their product.