AVR-Chat

One application of EEPROM I've done is to store frequency correction
data for DFS chips like the AD9854. The little canned oscillators are
never exactly on the frequency they specify, but the counter in the
DFS chip can be calibrated by zero-beating with a known accurate
frequency source. The calibration info is then stored in EEPROM and
read each time the circuit is powered up. As the oscillators drift
with age, it may need to be re-calibrated.

Zack

On 1/10/13, bayramdavies <Yahoo37849@ecrostech.com> wrote:
>
>
> --- In AVR-Chat@yahoogroups.com, Dave C  wrote:
>>
>> ... Flash, EEPROM, and SRAM ... not
>> clear on what each of these is used
>> for when writing a program ...
>
> Flash stores the program and fixed data.  It can only be modified by a
> special programming interface (ISP, JTAG, PDI, etc.) or by a special Flash
> Loader program residing in a special area of Flash memory.
>
> SRAM stores all data that will be modified at run time but does not need to
> survive a reset or power cycle, including all standard 'C' language
> variables (except automatic variables in registers).
>
> EEPROM can be used to store data that may be modified at run time but must
> survive a reset or power cycle.  Many applications don't use EEPROM at all,
> so you will probably ignore it at first.
>
> The AVR is a Harvard Architecture device, in the original sense of having
> separate address spaces for program and data memory.  As the 'C' language
> assumes Von-Neumann Architecture, i.e. a single address space for program
> and data, like the 68k, assembly language or non-standard features are
> necessary to get at data in Flash or EEPROM.
>
> Graham.
>
>
>