On Wed, Aug 26, 2009 at 08:21:00PM -0700, Parthasaradhi Nayani wrote: > David Kelly wrote: > > You are right that we know nothing about the application in question > > - details here would make it much easier to give recommendations. > > Hello all, > > I mentioned 4MB flash as it is the HW spec. This 4MB gets filled over > a period of time.
4 million bytes or bits? Most FLASH devices are sized by the bit. > Details of application - I have data packets each 32 bytes in size and > we have accommodate 2000 of these (predefined). 32 * 2000 = 6400 bytes. > This I plan to put in a part of the 4MB Flash. Rest of the memory will > be used for storing records comprising of these data packets with data > and time etc. The records will be deleted from time to time but the > data packets will remain. It is possible to use a long int as an > address pointer from the start of the available memory (after the data > packets) and store records. I still curious to know how one can create > a section larger than 64K. What you describe is probably best *not* mapped into avr-gcc name space or AVR address space. Is probably best to #define the starting offsets of each of your blocks of data. No matter what you do you won't be able to say *MyUInt16Ptr = 0x1234; you will have to write a routine and use it something like this: u16_value = 0x1234; result = Write4MBFlash( (uint32_t)MyUint16Ptr, sizeof(uint16_t), &u16_value ); All the external SPI FLASH devices I have used are paged. One read/writes to a RAM buffer in the device then flush that buffer to a page in FLASH. IIRC the Atmel device I last used had 264 byte pages which served to complicate addressing if one insisted on using all 264 bytes. Believe the designer's intent was that one use 256 bytes as a "sector" and the other 8 bytes for tracking usage, even linking to previous sector and next sector for a form of filesystem. Atmel had a very useful appnote containing C routines for access to their DataFlash parts which helped a lot. I felt the need to heavily edit it for style and naming convention. Rearranged a bit, and deleted a lot that I didn't use. But it was a very good start. -- David Kelly N4HHE, dke...@hiwaay.net ======================================================================== Whom computers would destroy, they must first drive mad. _______________________________________________ AVR-GCC-list mailing list AVR-GCC-list@nongnu.org http://lists.nongnu.org/mailman/listinfo/avr-gcc-list
