Example: How to Use Page Write Feature of I2C EEPROMs

[sayzer]

<font color="#000080"><i>' Omer YILDIZ , Istanbul/TURKEY
' May-2008
' Sayzer @ www.picbasic.co.uk/forum

' This code is to show how to use the page write feature of I2C eeproms.
' Page write feature allows us to write an entire page at one shot,
' and takes one write cycle to complete.
' This code will accept 128-byte packet from RS232 port @9600bps,
' and write the entire packet into 24C512 external eeprom at one shot.
' Incoming 128-bytes packets must have at least 15mS intervals.

' Page size is different from eeprom to eeprom.
' For example: Page size for 24C512 is 128 bytes while 
' it is 32 bytes for 24LC64.
' That means, we can write 128-bytes into the eeprom 
' at once and it takes only approx 5 - 10 ms.
' If we had to do this one byte at a time, we would have to wait 
' approx. 1 second to complete.
' 1 second may not sound that long but, 
' think about 64,000 byte waiting to be written !!

' PIC18F452
' Set your fuse settings up here.
</i><b>DEFINE </b></font>OSC <font color="#FF0000"><b>20

</b></font><font color="#000080"><i>'Thanks to DT
</i><b>INCLUDE </b></font><font color="#008000"><b>&quot;DT_INTS-18.bas&quot;    </b></font><font color="#000080"><i>' Base Interrupt System    
</i><b>INCLUDE </b></font><font color="#008000"><b>&quot;ReEnterPBP-18.bas&quot; </b></font><font color="#000080"><i>' Include if using PBP interrupts

'Thanks to Steve.
</i><b>DEFINE </b></font>HSER_RCSTA <font color="#FF0000"><b>90</b></font>h       <font color="#000080"><i>' Enable serial port &amp; continuous receive  
</i><b>DEFINE </b></font>HSER_TXSTA <font color="#FF0000"><b>24</b></font>h       <font color="#000080"><i>' Enable transmit, BRGH = 1
</i><b>DEFINE </b></font>HSER_SPBRG <font color="#FF0000"><b>129       </b></font><font color="#000080"><i>' 9600 Baud @ 0,16%
</i><b>DEFINE </b></font>HSER_CLROERR <font color="#FF0000"><b>1       </b></font><font color="#000080"><i>' Clear overflow automatically

'Thanks to MicroChip.
</i></font>ADCON1 = <font color="#FF0000"><b>7
</b></font>TrisA = <font color="#FF0000"><b>%000000
</b></font>TrisB = <font color="#FF0000"><b>%00000000
</b></font>TrisC = <font color="#FF0000"><b>%10000000   </b></font><font color="#000080"><i>'RC7 =&gt; RS232 RX (input pin).
</i></font>TrisD = <font color="#FF0000"><b>%00000000
</b></font>TrisE = <font color="#FF0000"><b>%000

</b></font>PortA = <font color="#FF0000"><b>0
</b></font>PortB = <font color="#FF0000"><b>0
</b></font>PortC = <font color="#FF0000"><b>0
</b></font>PortD = <font color="#FF0000"><b>0
</b></font>PortE = <font color="#FF0000"><b>0

</b></font>I2C_SCL   <font color="#000080"><b>VAR </b></font>PortC.<font color="#FF0000"><b>3
</b></font>I2C_SDA   <font color="#000080"><b>VAR </b></font>PortC.<font color="#FF0000"><b>4

</b></font>AdrW      <font color="#000080"><b>VAR WORD  </b><i>' Address variable for write operation.
</i></font>AdrR      <font color="#000080"><b>VAR WORD  </b><i>' Address variable for read operation.

</i></font>Mem       <font color="#000080"><b>VAR BYTE</b></font>[<font color="#FF0000"><b>1350</b></font>] <font color="#000080"><i>' Create an array as large as possible.
</i></font>RXFlag    <font color="#000080"><b>VAR BIT        </b><i>' Just a flag.

</i></font>Writetime <font color="#000080"><b>CON </b></font><font color="#FF0000"><b>15    </b></font><font color="#000080"><i>' This is the write cycle time for external eeprom. (mS)
</i></font>PageSize  <font color="#000080"><b>CON </b></font><font color="#FF0000"><b>128   </b></font><font color="#000080"><i>' Page size for 24C512 : 128 bytes; for 24LC64 : 32 bytes.


'====This is DT's famous and useful Int routine. =========
</i><b>ASM
</b></font><font color="#008000">INT_LIST  macro    </font><font color="#000080"><i>; IntSource,  Label,  Type, ResetFlag?
        </i></font><font color="#008000">INT_Handler   RX_INT,  _ReadPort,   PBP,  yes
    endm
    INT_CREATE           </font><font color="#000080"><i>; Creates the interrupt processor
</i><b>ENDASM

</b></font><font color="#008000">@ INT_ENABLE  RX_INT     </font><font color="#000080"><i>; Enable RX232 RX interrupt


</i></font>Begin:  <font color="#000080"><i>' Initial adr values are zero.
    </i></font>RXFlag  = <font color="#FF0000"><b>0          
    </b></font>AdrW    = <font color="#FF0000"><b>0        
    </b></font>AdrR    = <font color="#FF0000"><b>0

</b></font>Start:
    
    <font color="#000080"><b>I2CREAD </b></font>I2C_SDA, I2C_SCL,<font color="#FF0000"><b>$A1</b></font>,AdrR, [<font color="#000080"><b>STR </b></font>Mem\PageSize]    
     <font color="#000080"><i>' Read one page from EEPROM and store into mem array. 
    </i></font>AdrR = AdrR + PageSize   <font color="#000080"><i>'First  page: 0-127
                             'Second page: 0 +128   = 128 (128 - 255)
                             'Third  page: 128 +128 = 256 (256 - 383)
                                 '....etc..    
    ' Do your stuff ....
    
</i><b>GOTO </b></font>Start


ReadPort:
    <font color="#000080"><b>HSERIN </b></font>[<font color="#000080"><b>STR </b></font>Mem\PageSize]   
    <font color="#000080"><i>' Store 128-byte (0-127) incoming packet into Mem array.

    </i><b>I2CWRITE </b></font>I2C_SDA, I2C_SCL,<font color="#FF0000"><b>$A0</b></font>,AdrW,[<font color="#000080"><b>STR </b></font>Mem\PageSize]  
     <font color="#000080"><i>' Starting from addresss location = Adr, 
      ' ...write 128-byte mem elements into EEPROM at one shot. 
       '...Adr is the start address of the page in line.

    </i><b>PAUSE </b></font>Writetime   <font color="#000080"><i>' For 24C512, 15ms is more then good enough.
                      ' For LC series, 5-6 ms should be ok.
    </i></font>AdrW = AdrW + PageSize  
    <font color="#000080"><i>' For the next page write, increment EEPROM address 
     ' ...with the size of one page.  
  
    </i></font>RXFlag = <font color="#FF0000"><b>1            </b></font><font color="#000080"><i>' Set a flag for use in main loop.
    
</i></font><font color="#008000">@ INT_RETURN  



</font>

[Archangel]

Thanks Sayzer,
I will try this out.
JS

[Ioannis]

Hi Sayzer.

As the PBP manual states, the control byte must have bit 0 cleared. Is there any special reason that you have made it 1 in this command?

I2CREAD I2C_SDA, I2C_SCL,$A1,AdrR, [STR Mem\PageSize]

But here you still have it cleared:

I2CWRITE I2C_SDA, I2C_SCL,$A0,AdrW,[STR Mem\PageSize]

Regards,
Ioannis

[sayzer]

Hi Sayzer.

As the PBP manual states, the control byte must have bit 0 cleared. Is there any special reason that you have made it 1 in this command?

I2CREAD I2C_SDA, I2C_SCL,$A1,AdrR, [STR Mem\PageSize]

But here you still have it cleared:

I2CWRITE I2C_SDA, I2C_SCL,$A0,AdrW,[STR Mem\PageSize]

Regards,
Ioannis

Hi Ioannis,

The way I read the data sheet of 24C512 eeprom, the write bit is 0 and the read bit is 1.
Same as 24LC64, 24LC512 also.

I agree that it is confusing, but it is a fact that for read operation either 0 or 1 works anyway.

[Ioannis]

Yes, the data sheet clearly states that bit 0 defines read or write. But PBP manual on I2C commands, says that this bit must be kept at 0. May be the compiler takes care of it. Anyway, I am sure it works just fine.

Ioannis

[mister_e]

PBP handle the R/W bit for you.