eeprom problems : fm24C16A-P

ion

I am using an eeprom on my project and I found out some strange behaviors.
Some how , data written to a location with i2cout was written to multiple locations, at 256 bytes interval.
To test , I just put one i2cout command to address 0, value =1234, then I read all 2047 locations with a loop.
The sample code is at the end.
When I look at debug screen I can see at address 0,256,512 and so on ·,the read values was 1234.
What I do wrong ? I tried to replace the eeprom, with some other brand new one· ( I bought 10), and the result is the same. I spoke with the eeprom manufacturer Ramtron,
http://www.ramtron.com/ and they told me that is nothing wrong with the chip, the problem is how i2cout handle the protocol.
I need help please .
Thank you
·
' {$STAMP BS2pe}
' {$PBASIC 2.5}
' {$PORT COM2}
·
·
new········ VAR···· Word
addr······· VAR···· Word
VALUE······ VAR···· Word
·
VALUE=· 1234
·
·I2COUT 0, $A0, 0, [noparse][[/noparse]DEC4 value]
·DEBUG "DONE",CR
·
PAUSE 1000
Read_From_EEPROM:
· FOR addr = 0 TO 2047
I2CIN 0,$A1,ADDR, [noparse][[/noparse]HEX4· new]
··· DEBUG "Addr: " ,DEC4 addr, "·· ",
········· "READ: ", HEX4 new,CR
· ADDR=ADDR+3
· NEXT
· END
·
This is the short form of debug screen. I deleted the lines with 0000 in between

DONE
Addr: 0000·· READ: 1234
Addr: 0004·· READ: 0000
·
Addr: 0252·· READ: 0000
Addr: 0256·· READ: 1234
Addr: 0260·· READ: 0000
·
Addr: 0508·· READ: 0000
Addr: 0512·· READ: 1234
Addr: 0516·· READ: 0000
·
Addr: 0764·· READ: 0000
Addr: 0768·· READ: 1234
Addr: 0772·· READ: 0000
·
Addr: 1020·· READ: 0000
Addr: 1024·· READ: 1234
Addr: 1028·· READ: 0000
·
Addr: 1276·· READ: 0000
Addr: 1280·· READ: 1234
Addr: 1284·· READ: 0000
·
Addr: 1532·· READ: 0000
Addr: 1536·· READ: 1234
Addr: 1540·· READ: 0000
·
Addr: 1788·· READ: 0000
Addr: 1792·· READ: 1234
Addr: 1796·· READ: 0000

Jon Williams

The problem is how you're using I2COUT and I2CIN.· You have a device that requires two-byte syntax, but you're using one-byte syntax -- so your I2CIN statement is rereading the same 256-byte block.· You can fix your program with the correct syntax:

I2COUT 0, $A0, addr.BYTE1\addr.BYTE0, [noparse][[/noparse]DEC4 value]
 
I2CIN 0, $A1, addr.BYTE1\addr.BYTE0, [noparse][[/noparse]HEX4 new]

When in doubt, consult the Help file -- it will show you the correct syntax and examples for using it.


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Jon Williams
Applications Engineer, Parallax
Dallas Office

ion

Thank you Jon for the prompt reply. I tested the sample in the help file with the address 2050 and works fine. My question, is how I am sure that the "value" was not written to an other address. I know there is a sample program in the help, which I looked at it many times, but the syntax is too high for a beginner. What kind of simple loop to use to read the whole chip? And the second aspect is : Do I have to manually calculate the address by dividing with 256 every time·? What I do for example for address 12 or 159 ?
I still do not understand the mechanism of this i2c command. I thought that it will be simple to write i2cout and just put the location and the software will deal with low and high bytes.
Can you please send me a link where I can find more to read for a beginner. I have a nice collection of stamps books from Parallax, 6 or 7 but I did not find the answer to my question.
Thank you
Ion
·

Jon Williams

Our help file samples are meant to be as simple as possible without hiding the details of commands.

You can rerun your test program with the corrected syntax I showed you above and you should see that it is now correct. Here's how I would write it (using Parallax programming standards):

' {$STAMP BS2pe} 
' {$PBASIC 2.5} 
' {$PORT COM2} 



testVal    VAR    Word
eeAddr     VAR    Word
 
 
Setup:
  eeAddr = 0
  testVal = 1234
  I2COUT 0, $A0, eeAddr.BYTE1\eeAddr.BYTE0, [noparse][[/noparse]DEC4 testVal]
 
Main:
  DO
    I2CIN 0, $A1, eeAddr.BYTE1\eeAddr.BYTE0, [noparse][[/noparse]DEC4 testVal]
    DEBUG DEC4 eeAddr,  " : ", DEC4 testVal, CR
    eeAddr = eeAddr + 4
  LOOP WHILE (eeAddr < 2048)
  END

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Jon Williams
Applications Engineer, Parallax
Dallas Office

Post Edited (Jon Williams) : 8/18/2004 9:41:18 PM GMT

ion

jon,

here is the sample modified, but the result is the same.

new VAR Word

addr VAR Word

VALUE VAR Word

addr= 10

VALUE= 1234


I2COUT 0, $A0, addr.BYTE1\addr.BYTE0, [noparse][[/noparse]DEC4 value]
''I2COUT 0, $A0, 0, [noparse][[/noparse]DEC4 value]

DEBUG "DONE",CR



PAUSE 1000

Read_From_EEPROM:

FOR addr = 0 TO 2047

''I2CIN 0,$A1,ADDR, [noparse][[/noparse]HEX4 new]
I2CIN 0, $A1, addr.BYTE1\addr.BYTE0, [noparse][[/noparse]DEC4 new]

DEBUG "Addr: " ,DEC4 addr, " ",

"READ: ", DEC4 new,CR

ADDR=ADDR+3

NEXT

END

Wher i am wrong?
Thanks
Ion

Jon Williams

You may have written that data with bad code earlier. Write a little program that puts zero in every address, then run the other test. I don't have the device you're using, so I can't test the code myself.

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Jon Williams
Applications Engineer, Parallax
Dallas Office

ion

Sorry jon,

What i got on your answer just few minutes ago it is completly diferent then what i see now. Initialy it was my pieces of code, and now i see it is changed. Please disregard the previous reply

Thanks

IOn

Worapoht

coded you are talking to for 24C164 (can have more than 1 device per bus)
not 24C16 which partitioned to 8 pages of 256byte !
you may seen on datasheet that slave address not just $A0,
but $A2/$A4/$A6/$A8,$AC and $AE also used too..
is %1010 follow with A2 A1 A0 R/W..

then read code section should to be

Read_From_EEPROM:
FOR addr = 0 TO 2047
I2CIN 0,$A1+((addr/256)<<1),(ADDR//256), [noparse][[/noparse]HEX4 new] ' modified code here
DEBUG "Addr: " ,DEC4 addr, " ",
"READ: ", HEX4 new,CR
ADDR=ADDR+3
NEXT

ion

Thank you for explanation.
I will read the manual or data sheet more carefuly
Thanks again
Ion