Post by thread:Saving contents of a mcu to eeprom

Is there a way to save couple of bytes (8 or 10 bytes) to eeprom just before power outage? * I am using MPLAB C18 (the software is in C) * The unit is working with 220V AC converted to 12V DC then 5V DC. * Configuration bit is set so power on reset on, brown out detection on, brown out voltage 4.2, oscillator H4 (10MHz xtal working at 40MHz). I looked up the datasheet, according to page 27, I checked the RCON registers POR bit (that is the only one affected with brown out for some reason) and saved 8 bytes to eeprom if the POR bit was 1. I did this at the very first thing in the main() procedure. However, it did not work. Any ideas? If anyone is interested the product can be seen at: www.teksan.com.tr/vana.asp?L=E&Id=0401 or goto http://www.teksan.com.tr, select product then bathcing solutions. Thanks, Ömer YALHI spam_OUToyalhiTakeThisOuTteksan.com.tr http://www.teksan.com.tr/ Tel : +90 212 613 22 00 Fax: +90 212 544 70 35 -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email .....listservKILLspam@spam@mitvma.mit.edu with SET PICList DIGEST in the body

{Quote hidden}> -----Original Message----- > From: Ömer Yalhi [SMTP:oyalhiKILLspamTEKSAN.COM.TR] > Sent: Wednesday, January 15, 2003 11:18 AM > To: .....PICLISTKILLspam.....MITVMA.MIT.EDU > Subject: Saving contents of a mcu to eeprom > > Is there a way to save couple of bytes (8 or 10 bytes) to eeprom just > before power outage? > > * I am using MPLAB C18 (the software is in C) > * The unit is working with 220V AC converted to 12V DC then 5V DC. > * Configuration bit is set so power on reset on, brown out detection on, > brown out voltage 4.2, oscillator H4 (10MHz xtal working at 40MHz). > > I looked up the datasheet, according to page 27, I checked the RCON > registers POR bit (that is the only one affected with brown out for some > reason) and saved 8 bytes to eeprom if the POR bit was 1. I did this at > the very first thing in the main() procedure. However, it did not work. > Any ideas? > > If anyone is interested the product can be seen at: > www.teksan.com.tr/vana.asp?L=E&Id=0401 > or goto http://www.teksan.com.tr, select product then bathcing solutions. > > Thanks, > > Ömer YALHI > Check out the Low Voltage Detect (LVD) function. This is effectively a comparator with an adjustable reference set using the LVDCON register. If the supply falls below the reference voltage, and interrupt will be generated which you can capture and use to store you data. Ensure you have enough time remaing to store your 10bytes after the interrupt, the EEPROM memory typicaly takes 4ms per byte to write. Regards Mike ======================================================================= This e-mail is intended for the person it is addressed to only. The information contained in it may be confidential and/or protected by law. If you are not the intended recipient of this message, you must not make any use of this information, or copy or show it to any person. Please contact us immediately to tell us that you have received this e-mail, and return the original to us. Any use, forwarding, printing or copying of this message is strictly prohibited. No part of this message can be considered a request for goods or services. ======================================================================= Any questions about Bookham's E-Mail service should be directed to EraseMEpostmasterspam_OUTTakeThisOuTbookham.com. -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email listservspam_OUTmitvma.mit.edu with SET PICList DIGEST in the body

Hi Mike, LVD function works beatifully! Thanks. Ömer YALHI @spam@oyalhiKILLspamteksan.com.tr http://www.teksan.com.tr/ Tel : +90 212 613 22 00 Fax: +90 212 544 70 35 Check out the Low Voltage Detect (LVD) function. This is effectively a comparator with an adjustable reference set using the LVDCON register. If the supply falls below the reference voltage, and interrupt will be generated which you can capture and use to store you data. Ensure you have enough time remaing to store your 10bytes after the interrupt, the EEPROM memory typicaly takes 4ms per byte to write. Regards Mike ======================================================================= This e-mail is intended for the person it is addressed to only. The information contained in it may be confidential and/or protected by law. If you are not the intended recipient of this message, you must not make any use of this information, or copy or show it to any person. Please contact us immediately to tell us that you have received this e-mail, and return the original to us. Any use, forwarding, printing or copying of this message is strictly prohibited. No part of this message can be considered a request for goods or services. ======================================================================= Any questions about Bookham's E-Mail service should be directed to KILLspampostmasterKILLspambookham.com. -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email RemoveMElistservTakeThisOuTmitvma.mit.edu with SET PICList DIGEST in the body -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email spamBeGonelistservspamBeGonemitvma.mit.edu with SET PICList DIGEST in the body

Omer, This is what I would do. 1. find out minimum voltage that you think you want to save it when it gets below that suppose the voltage is 2,4 volts 2. connect one of your analog pin to read the voltage or external comparator if you are using digital input 3. in your eeprom reserve one byte to indicate there was a power surge suppose 0x00 is ok 0xFF is power surge 4. on your main code always read the pin and save to eeprom no matter what if it is reached below 2,4 then update surge register to 0xFF that way after it turned off and back on you will know about it. 4. if on your board there are other components that is part of eeprom data then you need to check them too to see how much time do you have to save every thing. Andre Abelian {Original Message removed}

One thing to be aware of is that as power drops, the data, address and control lines to devices may enter "undetermined" states. If the eeprom is still working at this low voltage, there is no telling what will happen. So maybe best not to leave the eeprom set to a address that has valid data (if that can happen). But do leave the control lines close to ground. Bill ----- Original Message ----- From: "Vmer Yalhi" <TakeThisOuToyalhiEraseMEspam_OUTTEKSAN.COM.TR> To: <RemoveMEPICLISTTakeThisOuTMITVMA.MIT.EDU> Sent: Wednesday, January 15, 2003 3:17 AM Subject: Saving contents of a mcu to eeprom Is there a way to save couple of bytes (8 or 10 bytes) to eeprom just before power outage? -- http://www.piclist.com hint: To leave the PICList piclist-unsubscribe-requestEraseME.....mitvma.mit.edu>

At 05:48 PM 1/16/03 -0800, you wrote: >One thing to be aware of is that as power drops, >the data, address and control lines to devices may >enter "undetermined" states. If the eeprom is >still working at this low voltage, there is no >telling what will happen. > >So maybe best not to leave the eeprom set to a >address that has valid data (if that can happen). >But do leave the control lines close to ground. 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" EraseMEspeffinterlog.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 RemoveMEpiclist-unsubscribe-requestEraseMEEraseMEmitvma.mit.edu>

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 removed}

At 04:57 AM 1/17/03 -0800, you wrote: >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. Sure, at least on the SPI ones and some others there is a /CE and/or a write-enable line that you can drive high or low and it will prevent writes. Anything that prevents writes in hardware from the point (voltage, and time) where the micro is last guaranteed to work perfectly to the point (voltage, time) where the memory is first guaranteed NOT to work will do the trick (but the latter voltage may not be on the data sheets). I once had to fix up a design where the thing worked perfectly in about 9 of 10 units in the field, but for about 10% of the micros, they would do something Not Good as they were powering down, and corrupt EEPROM. Needless to say, this was expensive for the manufacturer to fix, getting all those errant units back, not to mention the damage to their reputation in the market. >As to logging in general, a simple check sum of >the logged data would help insure it was valid >before it was used. Sure, or a CRC. Hamming codes are sexier, but when I looked into them they didn't match the patterns of corruption very well. Best regards, Spehro Pefhany --"it's the network..." "The Journey is the reward" RemoveMEspeffspam_OUTKILLspaminterlog.com Info for manufacturers: http://www.trexon.com Embedded software/hardware/analog Info for designers: http://www.speff.com -- http://www.piclist.com hint: PICList Posts must start with ONE topic: [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads