Posted on May 17, 2011 at 10:00Hi Hans,
If you are using the M25P64 (or same family) then you can use 'ssp_flash_driver.c' (from this site) to drive the IC. It has all the useful functions you need.
From a hardware point of view, the flash IC can be written 256 bytes at a time (flash 'page' size).
But to re-write, you first have to erase a flash 'sector' which is 65536 bytes in size.
One way (maybe simplest) would be to hold a 'sector' buffer (64KB) in RAM. Every time Read_Memory() or Write_Memory() is called, a 64KB sector can be read in or written out as required. For contiguous page reads/writes, this 64KB buffer can stay in RAM. Only when a 64KB boundary is reached, does an actual IC read/write have to take place.
Luckily, your MCU has enough RAM, provided you are not already using it for something else.
The logic in Read_Memory() and Write_Memory() needs to be changed to map 'Memory_Offset' onto 64KB chunks.
Although the flash IC allows you to write a page at a time (256 bytes), 'ssp_flash_driver.c' has a function that lets you write any number of bytes you want (including 64KB!). It's called 'SSP_FLASH_BufferWrite()'. This function will need to be modified slightly though, I think. It has a local variable called 'u8 NumofPage' which allows it operate over 256 pages. It might be safer to increase this to 'u16'?
So, as you can see, there is a bit of work needed to change the RAM-based example of UM0290 to work.
Regards,
Nick
