[Tinyos-help] InternalFlash question

[Aurélien Francillon]

hi Raj,

Le mardi 29 mai 2007 14:08, raj raj a écrit :
> Dear all,
>
>I am resending this email again as there has been no response to it. Please 
> help me with the following: 

http://www.catb.org/~esr/faqs/smart-questions.html

> raj raj <rajtos at yahoo.com> wrote: Dear all,
>
> In tinyos 1.1.x, there is a component called InternalFlashC which provides
> the interface InernalFlash. the avr platform has 128KB of program memory
> (flash memory), 4 KB of SRAM and 4 KB of EEPROM memory. The InternalFlashC
> componet can read from and write to internal Flash.My question is : What is
> internal Flash? Is it 4 KB of EEPROM or 128 KB of program memory. I think
> it should be 128KB of program memory. Am I right? I am getting confused
> with these terms.
>
> My next question is : What is the purpose of 4 KB of EEPROM ? Where is it
> used? Is there any component that can write to or read from 4 KB of EEPROM?

It's  the 4 KB of EEPROM internal to the atmega 128 (it's different from the 
external flash chip 512KB on serial port ),  you can see all of them on the 
general block diagram (figure 2 ) of atmega 128 at:
http://www.atmel.com/dyn/resources/prod_documents/doc2467.pdf

Access to the 128KB of program memory is more complex because you are 
potentially writing the code you are executing, If it's what you want, there 
is lots of details about this in the section "Boot Loader Support – 
Read-While-Write Self-Programming" . 
You can also have a look at the TOSBoot /Deluge which is doing just that ... 

If you really want to access the internal 4KB EEPROM:
1) Writing to it is _very_ slow 
2) Deluge is also using it, a few bytes for storing "permanent" data take care 
of that is you are using it see ps 
3) Use InternalFlashC to access it ...

In a way InternalFlashC should have been called InternalEEPROMC on mica 
platforms, but it may not be true for any platform ... 

Cheers 
Aurélien

PS: deluge  "iflash" usage 

$0000    IFLASH_BOUND_LOW <- begin of free space 
$0FE0    IFLASH_TOS_INFO_ADDR  <- end of free space , begin of deluge usage 
$0FE6    IFLASH_NODE_DESC_ADDR 
$0FF0    TOSBOOT_ARGS_ADDR 
$0FFF    IFLASH_BOUND_HIGH