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EEPROM read failure on 16F677 ?
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TopLoser
Guest
PostPosted: Thu Apr 30, 2009 3:41 pm     Reply with quote
The board is a very small custom designed double sided board with ground planes and very carefully laid out power. The power supply is very well designed (it's derived from a nominal 24v supply via a pre-regulator and then a 5v regulator). It's the very small square surface mount version of the 16F677 and has adequate decoupling. The board is professionally designed by a very large company and will be produced in large volumes in a commercial product - I'm not at liberty to say much more.

The company involved in the design use tens of thousands of PICs and have very good support directly from Microchip - but I'm now treating this as a potential compiler issue. I've reported it to CCS directly but have had no reply hence I've taken it onto this forum.

I myself have been writing embedded C code (and designing embedded systems and laying out boards) for over 25 years and have stumbled across all sorts of hardware and software related bugs.

I suppose I should start looking at the LST files next and trying to decipher that horrible assembly code that PICs use.

In fact - here's the code generated for the read_eeprom version

Code:

int8 c;
c = read_eeprom(1);

3001     MOVLW 0x1
1703     BSF 0x3, 0x6
008D     MOVWF 0xd
080C     MOVF 0xc, W
1303     BCF 0x3, 0x6
00A6     MOVWF 0x26


and the direct to registers version

Code:

#BYTE EEADR = 0x10d
#byte EEDAT = 0x10c
#BYTE EECON1 = 0x18c

#BIT EEPGD = 0x18c.7
#BIT RD = 0x18c.0

EEADR=1;
3001     MOVLW 0x1
1703     BSF 0x3, 0x6
008D     MOVWF 0xd

EEPGD=0;
1683     BSF 0x3, 0x5
138C     BCF 0xc, 0x7

RD=1;
140C     BSF 0xc, 0

c=EEDAT;
1283     BCF 0x3, 0x5
080C     MOVF 0xc, W
1303     BCF 0x3, 0x6
00A6     MOVWF 0x26


If anybody knows enough about PIC assembler to explain the differences I'd be grateful.
PCM programmer



Joined: 06 Sep 2003
Posts: 21708

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PostPosted: Thu Apr 30, 2009 4:08 pm     Reply with quote
Your code:
Quote:
int8 c;
c = read_eeprom(1);

3001 MOVLW 0x1
1703 BSF 0x3, 0x6
008D MOVWF 0xd
080C MOVF 0xc, W
1303 BCF 0x3, 0x6
00A6 MOVWF 0x26



This is the ASM code that I get in the .LST file with vs. 4.085:
Code:
.................... c = read_eeprom(1); 
001E:  MOVLW  01
001F:  BSF    03.6
0020:  MOVWF  0D
0021:  BSF    03.5
0022:  BCF    0C.7
0023:  BSF    0C.0
0024:  BCF    03.5
0025:  MOVF   0C,W
0026:  BCF    03.6
0027:  MOVWF  26


Here is the same thing, but in symbolic format:
Code:

.................... c = read_eeprom(1); 
001E:  MOVLW  01
001F:  BSF    STATUS.RP1
0020:  MOVWF  EEADR
0021:  BSF    STATUS.RP0
0022:  BCF    EECON1.EEPGD
0023:  BSF    EECON1.RD
0024:  BCF    STATUS.RP0
0025:  MOVF   EEDAT,W
0026:  BCF    STATUS.RP1
0027:  MOVWF  c

I notice that your list file uses commas in the BSF statements.
I was not able to duplicate that with any list file mode setting for
the CCS compiler. Are you even using the CCS compiler ?
TopLoser
Guest
PostPosted: Thu Apr 30, 2009 4:22 pm     Reply with quote
Yes I'm using CCS 4.085. I edited it slightly to remove what i thought was excess information.

actual LST file (as seen using "View, Disassembly listing" is

Code:

44:                   c = read_eeprom(1);
   0E2    3001     MOVLW 0x1
   0E3    1703     BSF 0x3, 0x6
   0E4    008D     MOVWF 0xd
   0E5    080C     MOVF 0xc, W
   0E6    1303     BCF 0x3, 0x6
   0E7    00A6     MOVWF 0x26
45:               
46:                   EEADR=1;
   0E8    3001     MOVLW 0x1
   0E9    1703     BSF 0x3, 0x6
   0EA    008D     MOVWF 0xd
47:                   EEPGD=0;
   0EB    1683     BSF 0x3, 0x5
   0EC    138C     BCF 0xc, 0x7
48:                   RD=1;
   0ED    140C     BSF 0xc, 0
49:                   c=EEDAT;
   0EE    1283     BCF 0x3, 0x5
   0EF    080C     MOVF 0xc, W
   0F0    1303     BCF 0x3, 0x6
   0F1    00A6     MOVWF 0x26


The format still isn't the same as yours, nor is the sequence of instructions generated by read_eeprom. I wish I knew why.
TopLoser
Guest
PostPosted: Thu Apr 30, 2009 4:35 pm     Reply with quote
Ok, just to make sure I've missed nothing out here is the full program and full assembler listing that I get. MPLAB IDE 8.20a, CCS PCM 4.085

Code:

#include <16F677.H>

#fuses INTRC_IO , NOWDT , NOBROWNOUT, NOMCLR, NOCPD
#use delay(clock=4000000)

#BYTE EEADR = 0x10d
#byte EEDAT = 0x10c
#BYTE EECON1 = 0x18c

#BIT EEPGD = 0x18c.7
#BIT RD = 0x18c.0

void main()
{
    int8 c;

   c = read_eeprom(1);

   EEADR=1;
   EEPGD=0;
   RD=1;
   c=EEDAT;

    while(1);
}


Code:

1:                 #include <16F677.H>
   000    3000     MOVLW 0
   001    008A     MOVWF 0xa
   002    2804     GOTO 0x4
   003    0000     NOP
2:                 
3:                 #fuses INTRC_IO , NOWDT , NOBROWNOUT, NOMCLR, NOCPD
4:                 #use delay(clock=4000000)
5:                 
6:                 #BYTE EEADR = 0x10d
7:                 #byte EEDAT = 0x10c
8:                 #BYTE EECON1 = 0x18c
9:                 
10:                #BIT EEPGD = 0x18c.7
11:                #BIT RD = 0x18c.0
12:               
13:                void main()
14:                {
   004    0184     CLRF 0x4
   005    301F     MOVLW 0x1f
   006    0583     ANDWF 0x3, F
   007    3061     MOVLW 0x61
   008    1683     BSF 0x3, 0x5
   009    008F     MOVWF 0xf
   00A    080F     MOVF 0xf, W
   00B    1283     BCF 0x3, 0x5
   00C    1703     BSF 0x3, 0x6
   00D    101F     BCF 0x1f, 0
   00E    109F     BCF 0x1f, 0x1
   00F    111F     BCF 0x1f, 0x2
   010    119F     BCF 0x1f, 0x3
   011    1303     BCF 0x3, 0x6
   012    131F     BCF 0x1f, 0x6
   013    3000     MOVLW 0
   014    1703     BSF 0x3, 0x6
   015    009E     MOVWF 0x1e
   016    0199     CLRF 0x19
   017    019A     CLRF 0x1a
   018    1683     BSF 0x3, 0x5
   019    019E     CLRF 0x1e
   01A    1283     BCF 0x3, 0x5
   01B    019B     CLRF 0x1b
   01C    1303     BCF 0x3, 0x6
   01D    128D     BCF 0xd, 0x5
15:                    int8 c;
16:               
17:                   c = read_eeprom(1);
   01E    3001     MOVLW 0x1
   01F    1703     BSF 0x3, 0x6
   020    008D     MOVWF 0xd
   021    080C     MOVF 0xc, W
   022    1303     BCF 0x3, 0x6
   023    00A6     MOVWF 0x26
18:               
19:                   EEADR=1;
   024    3001     MOVLW 0x1
   025    1703     BSF 0x3, 0x6
   026    008D     MOVWF 0xd
20:                   EEPGD=0;
   027    1683     BSF 0x3, 0x5
   028    138C     BCF 0xc, 0x7
21:                   RD=1;
   029    140C     BSF 0xc, 0
22:                   c=EEDAT;
   02A    1283     BCF 0x3, 0x5
   02B    080C     MOVF 0xc, W
   02C    1303     BCF 0x3, 0x6
   02D    00A6     MOVWF 0x26
23:               
24:                    while(1);
   02E    282E     GOTO 0x2e
   02F    0063     SLEEP


Your assembler output for the read_eeprom function matches exactly my direct to register code, and will work just fine (as you've observed before). Unfortunately my compiler forgets to generate quite a few lines when it creates the code for read_eeprom.

I'm losing a lot of confidence at the moment.
PCM programmer



Joined: 06 Sep 2003
Posts: 21708

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PostPosted: Thu Apr 30, 2009 4:40 pm     Reply with quote
Re-install the compiler.
TopLoser
Guest
PostPosted: Thu Apr 30, 2009 4:49 pm     Reply with quote
Ok, but CCS don't have historical version downloads available so I'll have to dig out backups to do that. I can't use the only version currently available for download (4.092) because that seems to be unable to deal with multiple compilation units in the same way all previous versions have.

Thank you for your patience and assistance so far.
Guest
EE read problems
PostPosted: Mon May 04, 2009 3:14 pm     Reply with quote
I have also have a similar problem reading internal EE in some 18F252 parts.

After programming, my PIC can't READ values from its internal EE, it looks just as if the EE is empty.

I can fix it if I do a READ of the EE locations using the PICkit2 after programming it. When I do this I can see that the EE did infact contain the values I expected, so I know it is being programmed correctly.

After doing this READ the application can then read the EE and it works fine from then on. It almost seems as if the programmer leaves the EE locked in some way and by performing this seperate READ with the PICstart, it unlocks it and kicks it back to life?

It does seem to vary from device to device because I first saw this some time ago and just thought I had a duff chip so I binned it. Things seemed fine for ages but now I've just come across a batch of 3 chips with this problem. Powering OFF/On does no good, but reading the EE with PICstart2 does fix them.

Any thoughts?
Thanks
PCM programmer



Joined: 06 Sep 2003
Posts: 21708

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PostPosted: Mon May 04, 2009 3:25 pm     Reply with quote
Post a very short test program that demonstrates the problem.
Also post your compiler version.

See this thread. It discusses an eeprom problem and shows how to
make a short test program to test it:
http://www.ccsinfo.com/forum/viewtopic.php?t=25612

Also look at articles on Pickit2 eeprom problems on the Microchip forum:
http://www.microchip.com/forums/tm.aspx?m=300966
http://www.microchip.com/forums/tm.aspx?m=172138
Guest
18F252 EE problem
PostPosted: Mon May 11, 2009 5:43 pm     Reply with quote
I have run this code in three different devices. In all 3 have problems reading the EE once programmed:

Dev#1 date code 0841
Dev#2 date code 0904
Dev#3 date code 0614

Device #1 and #2 both read 00 for all locations until you do a READ of the EE area using the pickit2 after this they will correctly read their EE contents. However once powered OFF they revert to not working until their EEs are READ again.

This is a new behaviour. Previously once they were working they stayed working even after power OFF/ON

Dev#3 reads 00 from all locations even after MCLRs are performed. Once you power OFF/ON it works fine, and will continue to work fine from then on. No READ of the EE with the PICkit 2 is required.

Here's the cut down code

Best regards
Rob
Code:
#include <C:\program files\picc\devices\18F252.h>
#device adc=8
#use delay(clock=4000000)
#fuses XT,PUT,BROWNOUT,NOWDT,NOLVP,WDT128,NOPROTECT,BORV45

#use
RS232(Baud=9600,Xmit=PIN_C6,rcv=PIN_C7,PARITY=N,BITS=8,RESTART_WDT,ERRORS) //ERRORS will clear any

#BYTE   EEADR    =      0xFA9      //holds addr of ee locn
#BYTE   EEDATA    =      0xFA8      //holds data for ee
#BYTE   EECON1    =      0xFA6      //ee access control reg
#BYTE   EECON2    =      0xFA7      //send codes to this reg to unlock ee


#ROM INT   0xF00000={'T'} 
#ROM INT 0xF00001={'E'}
#ROM INT 0xF00002={'S'}
#ROM INT 0xF00003={'T'}
#ROM INT 0xF00004={0x00}
#ROM INT 0xF00005={0x01}
#ROM INT 0xF00006={0x02}
#ROM INT 0xF00007={0x03}
#ROM INT 0xF00008={0x04}
#ROM INT 0xF00009={0x05}
#ROM INT 0xF0000A={0x06}
#ROM INT 0xF0000B={0x07}
#ROM INT 0xF0000C={0x08}
#ROM INT 0xF0000D={0x09}
#ROM INT 0xF0000E={0xAA}
#ROM INT 0xF0000F={0x55}

void main(void);
void read_ee();

void main(void)
{
   printf("\n\rContents of EE");
   read_ee();
}


void read_ee()
{
   int line_counter,i,ee_address,start_addr,stop_addr;
   int ee_rd_data;

   start_addr=0x00;
   stop_addr=0x3F;

   line_counter=0;
   for(i=start_addr;i<=stop_addr;i++)
   {
      ee_address=i;
      EEADR=i;                      //setup next ee address
      bit_clear(EECON1,7);         //select ee data memory
      bit_set(EECON1,0);         //initiate ee read
      ee_rd_data=EEDATA;         //fetch ee data

               if(line_counter==0)
      {
               printf("\r\n%X :",ee_address);
         line_counter=16;
      }
      line_counter--;
      printf("%X",ee_rd_data);
   }
}
Guest
18F252 EE problem
PostPosted: Mon May 11, 2009 5:47 pm     Reply with quote
Sorry I forgot to say that my compiler version is 3.242
Rob
PCM programmer



Joined: 06 Sep 2003
Posts: 21708

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PostPosted: Tue May 12, 2009 1:43 pm     Reply with quote
I was able to duplicate your problem. It's happening because you're not
setting up the CFGS bit in the EECON1 register. That bit controls whether
the Config register or the data eeprom/flash memory is accessed. It's
not initialized to anything upon power-up, according to the data sheet.
I added a line to your code to do this, and then it started working.
Quote:
EEADR=i; //setup next ee address
bit_clear(EECON1,6); // *** ADDED ***
bit_clear(EECON1,7); //select ee data memory
bit_set(EECON1,0); //initiate ee read
ee_rd_data=EEDATA; //fetch ee data

Question: The CCS read_eeprom() function already does it correctly.
It has that line in it. Why not just use the CCS built-in function ?
Guest
EE problems
PostPosted: Sun May 17, 2009 5:13 pm     Reply with quote
Thanks very much thats it!

Cant remember why I didnt use the in-built routines as that bit was written some time ago. Will use them from now.

Thanks again
Rob
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