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Hi Everyone,
I'm having some intermittent problems
writing to the data eeprom on 16F628 parts. Below is the code I'm using.
Once in a while, probably on the order of one in 2-3000 writes I'll get a
write failure which is when the data read back after a write does not match what
was written. There is decoupling caps at the chip and the supply looks solid.
I'd appreciate it if anyone could point out any problems with the following
code.
Thanks
Scott
; IN: NVMADDR = ADDRESS TO
WRITE
; W = DATA TO WRITE ; WRITENVM BSF STATUS, RP0 ; BANK 1 MOVWF _NVMDATA ; SAVE NEW BYTE ; GET CURRENT VALUE
MOVF _NVMADDR, W ; GET CURRENT VALUE MOVWF EEADR BSF EECON1, RD MOVF EEDATA, W XORWF _NVMDATA, W ; SAME AS CURRENT VALUE? BZ WRITENVMDONE ; YES, NO NEED TO CONTINUE MOVF EEDATA, W MOVWF _OLDNVMDATA ; SAVE CURRENT VALUE ; NEW VALUE DIFFERENT THEN CURRENT,
REPLACE
MOVF _NVMDATA, W ; NEW DATA CALL WRITENVMBYTE ; WRITE TO NVM SKPZ RETURN ; WRITE FAILED BSF STATUS, RP0 ; GET CURRENT CHECKSUM VALUE MOVLW LOW NVM_CHECKSUM ; CHECKSUM LOCATION MOVWF EEADR BSF EECON1, RD MOVF EEDATA, W ; READ CURRENT CHECKSUM SUBWF _OLDNVMDATA, F ; SUBTRACT OUT ORIGINAL VALUE NEGF _OLDNVMDATA, W ADDWF _NVMDATA, W ; ADD IN NEW VALUE AND WRITE UPDATE CHECKSUM BACK MOVWF EEDATA B WRITENVMBYTE1 ; WRITE & VERIFY BYTE TO NVM
LOCATION
WRITENVMBYTE BSF
STATUS,
RP0
; BANK 1
MOVWF EEDATA ; DATA TO WRITE MOVF _NVMADDR, W ; GET CURRENT VALUE MOVWF EEADR BCF INTCON, GIE ; DISABLE INTERRUPTS WRITENVMBYTE1
BSF EECON1,
WREN
; ENABLE WRITE MOD
MOVLW 55H MOVWF EECON2 MOVLW 0AAH MOVWF EECON2 ; UNLOCK BSF EECON1, WR ; START WRITE CYCLE BSF INTCON, GIE ; RE_ENABLER INT'S MOVF EEDATA, W WRITENVMBYTE2
CLRWDT
; FEED DOG WHILE WE WAIT
BTFSC EECON1, WR ; WRITE DONE? B WRITENVMBYTE2 ; NO. ; WRITE COMPLETE, READ BACK TO VERIFY BCF EECON1, WREN ; DISABLE WRITE MODE BSF EECON1, RD ; LATCH DATA FOR READ SUBWF EEDATA, W ; READ = WRITTEN? WRITENVMDONE BCF
STATUS, RP0
RETURN READNVM BSF
STATUS,
RP0
; BANK 1
MOVWF EEADR ; ADDRESS TO READ BSF EECON1, RD ; LATCH READ DATA MOVF EEDATA, W ; READ DATA BCF STATUS, RP0 ; BANK 0 RETURN __________________________________________
MavenWare SoftSystem Solutions 18 Ridge Road Clark, New Jersey 07066 USA Scott Kellish, Owner Tel. +01 732 382 1873 Fax: +01 732 382 1873 Mobile: +01 732 261-5856 e-mail: s...@comcast.net __________________________________________ |
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16F628 Data EEPROM Write Problem
Started by ●January 13, 2004
Reply by ●January 14, 20042004-01-14
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----- Original Message ----- From: "Scott Kellish" <> To: "PICLIST" <> Sent: Wednesday, January 14, 2004 2:15 AM Subject: [piclist] 16F628 Data EEPROM Write Problem Hi Everyone, I'm having some intermittent problems writing to the data eeprom on 16F628 parts. Below is the code I'm using. Once in a while, probably on the order of one in 2-3000 writes I'll get a write failure which is when the data read back after a write does not match what was written. There is decoupling caps at the chip and the supply looks solid. I'd appreciate it if anyone could point out any problems with the following code. Have you tried a battery supply? It might be something getting in via the mains. Leon -- Leon Heller, G1HSM Email: My low-cost Philips LPC210x ARM development system: http://webspace.webring.com/people/jl/leon_heller//lpc2104.html |
Reply by ●January 14, 20042004-01-14
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Thanks, This is a finished design already in the field. I posed the question about the supply stability to my EE counterpart and he feels its ok with ample decoupling caps, but he's going to take a look at it again. I just want to make sure that I'm not violating some timing constraint or sequencing with my code. Scott > > ----- Original Message ----- > From: "Scott Kellish" <> > To: "PICLIST" <> > Sent: Wednesday, January 14, 2004 2:15 AM > Subject: [piclist] 16F628 Data EEPROM Write Problem > > Hi Everyone, > I'm having some intermittent problems writing to the data eeprom on 16F628 > parts. Below is the code I'm using. Once in a while, probably on the order > of one in 2-3000 writes I'll get a write failure which is when the data read > back after a write does not match what was written. There is decoupling caps > at the chip and the supply looks solid. I'd appreciate it if anyone could > point out any problems with the following code. > > Have you tried a battery supply? It might be something getting in via the > mains. > > Leon > -- > Leon Heller, G1HSM > Email: > My low-cost Philips LPC210x ARM development system: > http://webspace.webring.com/people/jl/leon_heller//lpc2104.html > > to unsubscribe, go to http://www.yahoogroups.com and follow the instructions > > |
Reply by ●January 14, 20042004-01-14
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--- In , "Scott Kellish" <skellish@c...> wrote: > > Hi Everyone, > I'm having some intermittent problems writing to the data eeprom on 16F628 parts. Below is the code I'm using. If you are using the 16F628A there is a silicon errata on data EEPROM writes. It looks like uChip wants you to change to interrupt driven writing and to execute a SLEEP immediately after the "BSF EECON1, WR". I know you say you are using the non-A part and it doesn't look like the non-A part has the issue but I mention it because maybe you failed to properly specify the part you are using. As for the code, you do not have global interrupts disabled when you are writing your checksum -- that's dangerous as interrupt code may disturb the required instruction sequence during this operation. Move the "WRITENVMBYTE1" label up one line so it is before the "BCF INTCON, GIE" line. From your description, I doubt this is the problem you are experiencing but it is a potential source of problems. --Scott |
