Post by thread:[PIC:] Function to Write EEPROM

Hi guys, I have a program who uses EEPROM to store some strings for a menu. Until some hours ago, the menu didn't work and I was wondering why. I discovered that the procedure that writes to the EEPROM the strings received was causing the trouble and if I comment it, all the rest works fine. I use a 16F877A PIC and the code for the function is as follows: void eeprom_wr(unsigned char addr, unsigned char value) { while(WR)continue; // addr &= 0x7F; EEADR=addr; EEDATA=value; EEPGD = 0; WREN=1; CARRY=0; if(GIE)CARRY=1; GIE=0; EECON2=0x55; EECON2=0xAA; WR=1; WREN=0; if(CARRY) GIE=1; EEIF = 0; } Now I cannot imagine the reason for which the function causes the program to hang or to act abnormally. The EEPGD bit is cleared, so it is not writing to the flash. Any suggestions are more than welcomed... Lucian Copat -- http://www.piclist.com hint: PICList Posts must start with ONE topic: [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads

{Quote hidden}>-----Original Message----- >From: Lucian [spam_OUTlucifferTakeThisOuTHOME.RO] >Sent: 21 May 2004 15:30 >To: .....PICLISTKILLspam@spam@MITVMA.MIT.EDU >Subject: [PIC:] Function to Write EEPROM > > >Hi guys, > >I have a program who uses EEPROM to store some strings for a >menu. Until some hours ago, the menu didn't work and I was >wondering why. I discovered that the procedure that writes to >the EEPROM the strings received was causing the trouble and if >I comment it, all the rest works fine. I use a 16F877A PIC and >the code for the function is as follows: > >void eeprom_wr(unsigned char addr, unsigned char value) { > > while(WR)continue; >// addr &= 0x7F; > EEADR=addr; > EEDATA=value; > EEPGD = 0; > WREN=1; > > CARRY=0; > if(GIE)CARRY=1; > GIE=0; > > EECON2=0x55; > EECON2=0xAA; > > WR=1; > WREN=0; > if(CARRY) > GIE=1; > EEIF = 0; >} > >Now I cannot imagine the reason for which the function causes >the program to hang or to act abnormally. The EEPGD bit is >cleared, so it is not writing to the flash. Any suggestions >are more than welcomed... > >Lucian Copat Are you writing several bytes to the eeprom? This function waits for each byte to be written before returning, and at 4~5ms per byte, it's possible that you are getting a watchdog timeout, especialy if the watchdog pre-scaler is 1:1 which gives an ~18ms timeout. 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 postmasterKILLspambookham.com. -- http://www.piclist.com hint: PICList Posts must start with ONE topic: [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads

>I observed now that the problem happens when I write more than one byte >in a burst. If I only write the first letter of each option, it works... >It's strange...should I put a delay after each write ? Most definitely. In fact if you look at the example code in the data sheet it tells you to check to see if the eeprom portion is busy writing before doing the next write - at least this is the case for 16F series, haven't checked the 18f series, but I am not aware of any technology changes in this area. -- http://www.piclist.com hint: PICList Posts must start with ONE topic: [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads

>-----Original Message----- >From: Alan B. Pearce [.....A.B.PearceKILLspam.....RL.AC.UK] >Sent: 21 May 2004 16:27 >To: EraseMEPICLISTspam_OUTTakeThisOuTMITVMA.MIT.EDU >Subject: Re: [PIC:] Function to Write EEPROM > > >>I observed now that the problem happens when I write more >than one byte >>in a burst. If I only write the first letter of each option, it >>works... It's strange...should I put a delay after each write ? > >Most definitely. In fact if you look at the example code in >the data sheet it tells you to check to see if the eeprom >portion is busy writing before doing the next write - at least >this is the case for 16F series, haven't checked the 18f >series, but I am not aware of any technology changes in this area. The function that the OP listed previously waits for the eeprom's busy flag to clear before attempting a wite, so a delay should not be required. The function looks very much like the one used in HiTech PICC, and I have used this many times to write a string of bytes to the EEPROM with no problem. If the watchdog is definitely disabled, then I see no reason for this code sequence to cause problems. 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 postmasterspam_OUTbookham.com. -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email @spam@listservKILLspammitvma.mit.edu with SET PICList DIGEST in the body