> -----Original Message----- > From: linuxppc-embedded-bounces at ozlabs.org > [mailto:linuxppc-embedded-bounces at ozlabs.org] On Behalf Of > J?n Benediktsson > Sent: Friday, November 05, 2004 9:14 AM > To: Wolfgang Denk > Cc: linuxppc-embedded at ozlabs.org > Subject: Re: Handling power failure - MPC5200 > > > In message <OF368071C2.FBC6B7BC-ON00256F42.003F3DF3-00256F42. > > 0044E8BB at marel.is> you wrote: > > > > > > Capacitors on the supply provide me with some > milliseconds to repond > to > > > power failure, which I would > > > like to use to do as much cleanup as possible before power is > > > totally gone. In particular, I am concerned > > > > How many is "some"? If it's not >100 or so it is probably > not worht > > the effort... > > With the current design "some" is <50, but we can change the > design if we find it necessary. > > > > > Use the standard methods: use the CF card read-only (many > CF cards > > can be damaged [beyond repair] when you power off > while a write > > operation is in progress). > > Is this an acknowledged fact by CF manufacturers or based on > experiece ? > > Thank you very much for your input. > > Regards, > J?n Benediktsson > Marel hf.
Hi J?n, Read the CF card detailed specifications carefully (and if it ain't in writing, it ain't real). What I've seen is marketing bullet points saying the cards can survive a power loss event with no loss of data, but when I read the detailed CF specification, the disclaimer was that power had to be held up for X mSec (I forgot what X was, 2mSec or 10mSec most likely) after the last write operation. The marketing bullet point was exactly that: marketing. The real requirement levied on the user (you) was that you had to have X mSec power hold up after the last write operation (i.e. a X mSec power fail warning with no write operations after the PF warning). The hold-up requirement gave the CF internals enough time to complete a flash write cycle. gvb ****************************************** The following messages are brought to you by the Lawyers' League of IdioSpeak: ****************************************** The information contained in, or attached to, this e-mail, may contain confidential information and is intended solely for the use of the individual or entity to whom they are addressed and may be subject to legal privilege. If you have received this e-mail in error you should notify the sender immediately by reply e-mail, delete the message from your system and notify your system manager. Please do not copy it for any purpose, or disclose its contents to any other person. The views or opinions presented in this e-mail are solely those of the author and do not necessarily represent those of the company. The recipient should check this e-mail and any attachments for the presence of viruses. The company accepts no liability for any damage caused, directly or indirectly, by any virus transmitted in this email. ******************************************
