Hi guys,

I'm working on a file system for cmdOS, and I want every files to be in archive to allow user programs to use a maximal amount of free RAM. I planned to handle it this way :

• A 3-bytes pointer on a VAT at a static address in RAM consisting of a 2-bytes address (low byte then high byte) and a page number.
• At the location pointed to by this pointer and in the given flash page, the start of the VAT.
• After this location, each and every file whose structure will be discussed later.

The problem is : I don't know how to write to flash. I know how to swap pages using ports 6 and 7, but I also know that you can't just write to the corresponding areas like that.

How can I, say, write a byte to a flash page ?

Note that I don't have any built-in routine for that. I'm NOT using the TI-OS nor any library, and I don't want to. I just want to understand how to do that and then being able to implement it.

How can I, say, write a byte to a flash page ?

That is not a good idea. The flash can't bear an infinite number of writes. That number is high (10000 or something) so in "normal conditions of use", you don't reach it, but if you plan on writing byte per byte, or even 10 bytes per 10 bytes, as long as you use it often, you have more chance of having a flash wear.

Also, sorry not to actually answer the question (), I think that you should ask thepenguin or DrDnar or Runer or other people like that about unlocking flash.

Well, if you can only erase sectors, how can you save datas into them ?

And btw I won't be able to understand a code which does something I don't know anything about.

How could I have missed that, I read every page of Ti-83+:OS on WikiTi (well, I thought)

Thanks a lot, that'll help me

Yup, the raw commands are in the datasheet, which is why I suggested him to read the datasheet and then find the corresponding routines in TI's boot code
But if it's documented in WikiTI, even better.

Writing more than one byte is just a matter of embedding the code for writing a byte into a loop. As I wrote above, what wears out the Flash memory is erasing it, not writing to it.

Yup, erasing a sector is necessary so that you can write again arbitrary data to it. When writing to Flash memory (both NOR and NAND), the write operation is effectively an AND operation: it can only turn bits from 1 (default state after erasing) to 0. Only erasing makes it possible to turn bits from 0 to 1, but erasing is a slow, bulk operation performed over large blocks (sectors).

Only if you want to overwrite it. If you have erased the sector (a chunk of 4 flash pages), you can write to all of the bytes. That is why the OS needs to garbage collect. When you unarchive to edit, then rearchive, it gets written back to a different place instead of overwriting the whole sector just to replace the data.