Ronald G Minnich wrote:
> On 23 May 2001, Eric W. Biederman wrote:
>
>
>>> We're talking about it here. We call it "resurrection". Old core-memory
>>> machines used to do this all the time.
>>
>> It will be interesting to see if we can do anything with this. This
>> is very dangerous teritory to go into though. One mistake and you are likely
>> to loose more than with exisiting systems.
>
>
> I would guess you are right. It's one of those weird "wouldn't it be nice"
> type things.
>
> ron
Thats why micron came out with SyncFlash. Flash with SDRAM compatible
timing. So you can even loose power and retain memory.
For standard SDRAM from Micron the following would apply:
The SELF REFRESH command can be used to retain
data in the SDRAM, even if the rest of the system is
powered down. When in the self refresh mode, the
SDRAM retains data without external clocking.
The SELF REFRESH command is initiated like an AUTO
REFRESH command except CKE is disabled (LOW).
Once the SELF REFRESH command is registered, all the
inputs to the SDRAM become "Don't Care," with the
exception of CKE, which must remain LOW.
Once self refresh mode is engaged, the SDRAM
provides its own internal clocking, causing it to perform
its own AUTO REFRESH cycles. The SDRAM must
remain in self refresh mode for a minimum period
equal to t RAS and may remain in self refresh mode for
an indefinite period beyond that.
The procedure for exiting self refresh requires a
sequence of commands. First, CLK must be stable (stable
clock is defined as a signal cycling within timing
constraints specified for the clock pin) prior to CKE
going back HIGH. Once CKE is HIGH, the SDRAM must
have NOP commands issued (a minimum of two clocks)
for t XSR, because time is required for the completion of
any internal refresh in progress.
Upon exiting the self refresh mode, AUTO REFRESH
commands must be issued every 15.625�s or less as
both SELF REFRESH and AUTO REFRESH utilize the row
refresh counter.
If you could get a chipset to adhere to the spec when jumping between
auto and self refesh modes it would work.
Bari
