AVR-Chat

Moataz Hussein wrote:
> Hello,
> I am building a data logging system to record temperaure readings and
> store them on a flash. 
> I am using ATmega 16 and AT45DB161D memory.
> I have some points which are not clear though I studied the ATDB161
> datasheet. 
> 
> 
> Please correct me.
> How can I write for example 10 bytes of data to the memory? then
> store another 10 bytes after the first 10 bytes? 
> I will give command to write page through buffer and send the first
> 10 bytes, which will be stored in page 1 for example. How to do the
> next step?  
> 
> 
> How can I read the 20 bytes which are prevoiusly stored?
> I will send a command to read the page the contain the stored data,
> checking the SPIF when set read the first byte and so on.. 
> 
> 
> I Have to check SPIF after each byte to be sure that it is sent or
> recieved? 

The AT45DB... dataflash chips have a RAM buffer to temporarily store
data before you write it to the flash (or when reading it from the
flash). But the flash can only be written in a whole page of 524 (? I
think) bytes.

So you have 2 options, you can either fill the ram buffer before you
write the flash page all in one go, or you need to read back the flash
page into the buffer, modify your 10 bytes and write it back to the
flash again.

The first way is best if you can be sure you are not going to lose
power. The second way will mean you don't lose data if the power is
turned off but will mean more "wear" of the flash.

The commands for read block to buffer, write block to buffer etc are all
listed in the data sheet.

If you are writing or reading a sequence of bytes to or from the RAM
buffer, you don't have to check SPIF each time - just once before you
start to make sure the chip is not busy with a flash write or erase
operation.


-- 
Tim Mitchell

Thanks Tim for your advice,

Actualy I was not able at all to find helpful material concering that, but
at last I found and application note AVR335 which has some hints.
Will continue testing ,

Moataz


On Tue, Sep 9, 2008 at 9:58 AM, Tim Mitchell <tim@sabretechnology.co.uk>wrote:

>     Moataz Hussein wrote:
> > Hello,
> > I am building a data logging system to record temperaure readings and
> > store them on a flash.
> > I am using ATmega 16 and AT45DB161D memory.
> > I have some points which are not clear though I studied the ATDB161
> > datasheet.
> >
> >
> > Please correct me.
> > How can I write for example 10 bytes of data to the memory? then
> > store another 10 bytes after the first 10 bytes?
> > I will give command to write page through buffer and send the first
> > 10 bytes, which will be stored in page 1 for example. How to do the
> > next step?
> >
> >
> > How can I read the 20 bytes which are prevoiusly stored?
> > I will send a command to read the page the contain the stored data,
> > checking the SPIF when set read the first byte and so on..
> >
> >
> > I Have to check SPIF after each byte to be sure that it is sent or
> > recieved?
>
> The AT45DB... dataflash chips have a RAM buffer to temporarily store
> data before you write it to the flash (or when reading it from the
> flash). But the flash can only be written in a whole page of 524 (? I
> think) bytes.
>
> So you have 2 options, you can either fill the ram buffer before you
> write the flash page all in one go, or you need to read back the flash
> page into the buffer, modify your 10 bytes and write it back to the
> flash again.
>
> The first way is best if you can be sure you are not going to lose
> power. The second way will mean you don't lose data if the power is
> turned off but will mean more "wear" of the flash.
>
> The commands for read block to buffer, write block to buffer etc are all
> listed in the data sheet.
>
> If you are writing or reading a sequence of bytes to or from the RAM
> buffer, you don't have to check SPIF each time - just once before you
> start to make sure the chip is not busy with a flash write or erase
> operation.
>
> --
> Tim Mitchell
>
> 
>


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