memory calculations for embedded linux on ARM cortex

Hi,

I want to have embedded linux with C++ application on 32 bit ARM cortex based microcontroller.(price < $20)

I got to know through google search that I need to use the external RAM and FLASH.

I would like to know what would be the memory requirements (On board RAM, ROM and external RAM and Flash) of such application?

Suggest any links for study

You've stated no application, no one can suggest anything unless you know how much memory your application will need. You can search Google for low profile embeded linux's to get an idea of their memory footprint for the OS, but what the application uses is entirely up to you.

Your best bet would actually to see how others do it. Search on BeagleBoard, Raspberry Pi. One of my most favorite sites for this is:

https://free-electrons.com/training/embedded-linux/

More: https://www.electro-tech-online.com/custompdfs/2012/05/arm-linux.pdf

Hi,
If you need Linux with ARM you need to choose any one equal to or above ARM9. Below ARM 9 you can not work with Linux.