Spehro, I have never designed a circuit with power fail capacity. Sounds like you have. so I appreciate what you say. The case I am relating to was where I had nothing to do with the design of the circuits, not that I would have done anything different. It was designed 20 years or so ago and had a 2k byte by 8 bit static memory that was battery backup. This memory was the only ram on the board so it was used for logging as well as everything else. The power supply was powered through the micro switch interlock for the cover that would be opened often. Now I know that this means "trouble" is ahead. So when power went off, the ram was still functioning, and if the chip select and read/write lines were in the proper state, the ram would write the unspecified data lines into the memory depending on what order the address lines dropped power. Actually seen the results in the ram chip one time. So I would now try to insure that random stuff on the lines could not affect the logging device as power drops. Would it be possible to load the chip select line so it goes to a safe state before power drops all the way? No need to answer as I know nothing about eeproms and do not intend to design a circuit. As to logging in general, a simple check sum of the logged data would help insure it was valid before it was used. Bill ----- Original Message ----- From: "Spehro Pefhany" To: Sent: Thursday, January 16, 2003 6:33 PM Subject: Re: Saving contents of a mcu to eeprom > The *safe* thing to do is to force a reset on the PIC before it > enters such uncharted territory. Anything else and he's gambling. > > Best regards, > > Spehro Pefhany --"it's the network..." "The Journey is the reward" > speff@interlog.com Info for manufacturers: http://www.trexon.com > Embedded software/hardware/analog Info for designers: http://www.speff.com > > -- > http://www.piclist.com hint: To leave the PICList > mailto:piclist-unsubscribe-request@mitvma.mit.edu -- http://www.piclist.com hint: PICList Posts must start with ONE topic: [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads