How to read & write to a 25aa1024 (1 Mbit SPI Bus Serial EEPROM) via 16F88

[Dave]

wolwil, Here it is again incase you didn't find it. Maxpages is set for 1023 x the number of 24LC1025's you have connected. The routine saves the last storage pointer in the last 2 locations of the last 24LC1025. Block is incremented once for each page. Before you start a clean write you would set block to 0 which is the first page. When you want to read back the data then you would call READ_WRITE_BLK1025 and block would have the last address written..

This routine is rock solid and I use it for accessing 4 x 24LC1025's for a total of over 4 gigabits of memoy to record Azmnuth,Elevation,East/West/Up/Down Sensor data and control flag information for about 2 months at 1 minute intervals... I hope this helps...

 
CNTRL_BYTE    CON    $A0        'CONTROL BYTE FOR 24LC1025 I2C EEPROM MEMORY (A0/A1 USED FOR CHIP SELECT)
MAX_PAGES    CON    4095    'MAXIMUM MEMORY STORAGE PAGES,(32 BYTES/MINUTE x 4 MINUTES x PAGES = TOTAL MINUTES)
 
'*********************************************************************
RW_EEPROM1025:        'READ FROM or WRITE TO SERIAL EEPROM
'*********************************************************************
    IF READ_WRITE = 1 THEN    'WRITE 128 BYTE BLOCK TO EEPROM
        IF BLOCK <> 0 THEN    'IF STARTING NEW PASS DON'T READ OLD LOCATION
            READ_WRITE = 0    'SET FOR BLOCK READ
            GOSUB READ_WRITE_BLK1025    'READ FROM SERIAL EEPROM NEXT AVAILABLE STORAGE BLOCK
            READ_WRITE = 1    'SET FOR BLOCK WRITE
        ENDIF
        DEVICE = BLOCK / 512    'SELECT WHICH PHYSICAL ADDRESS BOUNDRY & EEPROM
        ADDRESS = BLOCK << 7    'CALCULATE 12C ADDRESS TO STORE DATA TO
        CNTROL_BYTE = CNTRL_BYTE    'COPY CONTROL BYTE
        CNTROL_BYTE.1 = DEVICE.1    'SET LSB OF HARDWARE ADDRESS
        CNTROL_BYTE.2 = DEVICE.2    'SET MSB OF HARDWARE ADDRESS
        CNTROL_BYTE.3 = DEVICE.0    'SET 64K BLOCK BIT
        INTCON.7 = 0    'CLEAR GLOBAL INTERRUPT
        I2CWRITE SDA,SCL,CNTROL_BYTE,ADDRESS,[STR STOR_DATA\128]    'SAVE DATA TO 12C
        WRITEOCCURED = 1
        INTCON.7 = 1    'SET GLOBAL INTERRUPT
        PAUSE 6        'ALLOW TIME FOR I2C WRITE ~5Ms.
        BLOCK = BLOCK + 1    'INCREMENT FOR NEXT AVAILABLE BLOCK TO WRITE
        BLOCK = BLOCK MIN MAX_PAGES    'LIMIT TO n BLOCKS OF 128 BYTES
        GOSUB READ_WRITE_BLK1025    'WRITE TO or READ FROM SERIAL EEPROM LAST STORAGE BLOCK
    ELSE
        DEVICE = BLOCK / 512    'SELECT WHICH PHYSICAL ADDRESS BOUNDRY & EEPROM
        ADDRESS = BLOCK << 7    'CALCULATE 12C ADDRESS TO STORE DATA TO
        CNTROL_BYTE = CNTRL_BYTE    'COPY CONTROL BYTE
        CNTROL_BYTE.1 = DEVICE.1    'SET LSB OF HARDWARE ADDRESS
        CNTROL_BYTE.2 = DEVICE.2    'SET MSB OF HARDWARE ADDRESS
        CNTROL_BYTE.3 = DEVICE.0    'SET 64K BLOCK BIT
        INTCON.7 = 0    'CLEAR GLOBAL INTERRUPT
        I2CREAD SDA,SCL,CNTROL_BYTE,ADDRESS,[STR READ_DATA\128]    'LOAD IN ENTIRE BLOCK
        WRITEOCCURED = 1
        INTCON.7 = 1    'SET GLOBAL INTERRUPT
    ENDIF
    RETURN
 
'*********************************************************************
READ_WRITE_BLK1025:    'WRITE TO or READ FROM SERIAL EEPROM NEXT AVAILABLE STORAGE BLOCK
'*********************************************************************
    ADDRESS = 65534        'POINT TO LAST STORED DATA(WORD) ADDRESS
    DEVICE = MAX_PAGES / 512    'SELECT WHICH PHYSICAL ADDRESS BOUNDRY & EEPROM
    CNTROL_BYTE = CNTRL_BYTE    'COPY CONTROL BYTE
    CNTROL_BYTE.1 = DEVICE.1    'SET LSB OF HARDWARE ADDRESS
    CNTROL_BYTE.2 = DEVICE.2    'SET MSB OF HARDWARE ADDRESS
    CNTROL_BYTE.3 = DEVICE.0    'SET 64K BLOCK BIT
    IF READ_WRITE = 1 THEN
        INTCON.7 = 0    'CLEAR GLOBAL INTERRUPT
        I2CWRITE SDA,SCL,CNTROL_BYTE,ADDRESS,[BLOCK.LOWBYTE,BLOCK.HIGHBYTE]    'WRITE DATA POINTER TO 12C    
        WRITEOCCURED = 1
        INTCON.7 = 1    'SET GLOBAL INTERRUPT
        PAUSE 6        'ALLOW TIME FOR I2C WRITE ~5Ms.
    ELSE
        INTCON.7 = 0    'CLEAR GLOBAL INTERRUPT
        I2CREAD SDA,SCL,CNTROL_BYTE,ADDRESS,[BLOCK.LOWBYTE,BLOCK.HIGHBYTE]    'READ DATA POINTER FROM 12C    
        WRITEOCCURED = 1
        INTCON.7 = 1    'SET GLOBAL INTERRUPT
    ENDIF
    RETURN

Dave Purola,
N8NTA

[mackrackit]

Hi Dave,
Thanks for posting your code. I also found my problem...

My problem is "I am a newbe!!!".
I forgot PORTF.6 on the 18F6680 is an analog pin.
RTFD RTFD RTFD

For what it is worth.. When I take care of the analog issue I can read the part with SHIFTIN/OUT. I can not write to the part that way yet. Still have a timing problem I guess. It may not be worth messing with other than an exercise in coding.

[wolwil]

CNTRL_BYTE CON $A0 'CONTROL BYTE FOR 24LC1025 I2C EEPROM MEMORY (A0/A1 USED FOR CHIP SELECT)

Maybe this is where I am getting confused... you have the control byte being $A0 which is basically saying to write to the 24LC1025 seeing how the read write bit in that is a 0 like this "10100000" but the you say in your comment that the A0/A1 is for chip select...So in this following line of code where I have the $A0 is that the 8 bit control byte or just the Chip Select portion of it???

I2CREAD PORTB.1,PORTB.4,$A0,addr,[B1]

See I thought if I wanted to write to chip select A1 I needed to use $A2 or in binary like this %10100010 and if I wanted to read from it I needed to use $A3 or in binary like this %10100011.

Every combination to read and write to all 4 Chips:

%10100000 or $A0 = Write to A0 (Pins A0 & A1 Tied Low)
%10100001 or $A1 = Read from A0
%10100010 or $A2 = Write to A1 (Pins A0 Tied Low & A1 Tied High)
%10100011 or $A3 = Read from A1
%10100100 or $A4 = Write to A2 (Pins A0 Tied High & A1 Tied Low)
%10100101 or $A5 = Read from A2
%10100110 or $A6 = Write to A3 (Pins A0 and A1 Tied High)
%10100111 or $A7 = Read from A3

So with me having both A0 and A1 Pins Tied to ground I should be using the first 2 options when trying to read/write to the chip or am I just way off on this???

Am I incorrect in my thinking of what PBP is calling the Control Byte???

[mackrackit]

10100000
Is the R/W bit. Leave it as "0" and PBP takes care of parsing it to a "1" if needed.

10100000
Are the A0 and A1 bits. If pins A0 and A1 are connected to the zero rail leave as zero. Mixing and matching on or the other or both gives the four combination's for up to four chips on the same bus.

10100000
Is the bit to set to read or write to the first or second block.

[mackrackit]

Here is how to read and write to a Serial EEPROM using SHIFTIN/SHIFTOUT.
Using a 24FC1025.

Why???? Why not???

I have the DATA and CLOCK pins pulled up with 2.7k resistors.
Follow the code with the data sheet to understand what is going on.

DEFINE OSC 20

DPIN    VAR PORTB.2    'I2C DATA PIN
CPIN    VAR PORTB.1    'I2C CLOCK PIN
CONT1   CON %10100001  'READ CONTROL
CONT0   CON %10100000  'WRITE CONTROL
ADDR_HB   VAR BYTE
ADDR_LB    VAR BYTE
DATOW       VAR BYTE
ACK            VAR BIT
ADDR_HB = 0'%00000000
ADDR_LB = 0'%00000000
DATOW    VAR BYTE
CNT VAR BYTE
CNT = 0

START:
    CNT = CNT + 1
    DATOW = 245
    GOSUB WRITE_DATA
    PAUSE 10
    GOSUB READ_DATA
    LCDOUT $FE,1,"TEST ",DEC CNT
    lcdout $FE,$C0,"DATA IN ",DEC DATI
    lcdout $FE,$90,"LB ",DEC ADDR_LB
    PAUSE 250
    GOTO START
    
    WRITE_DATA:     
    ADDR_LB = ADDR_LB + 1
    GOSUB START_ROM
    SHIFTOUT DPIN,CPIN,1,[CONT0]
    SHIFTIN DPIN,CPIN,0,[ACK\1]
    SHIFTOUT DPIN,CPIN,1,[ADDR_HB]
    SHIFTIN DPIN,CPIN,0,[ACK\1]
    SHIFTOUT DPIN,CPIN,1,[ADDR_LB]
    SHIFTIN DPIN,CPIN,0,[ACK\1]
    SHIFTOUT DPIN,CPIN,1,[DATOW\8]      
    SHIFTOUT DPIN,CPIN,1,[%1\1]
    GOSUB STOP_ROM
    PAUSE 10
    RETURN
    
    READ_DATA: 
    GOSUB START_ROM
    SHIFTOUT DPIN,CPIN,1,[CONT0]
    SHIFTIN DPIN,CPIN,0,[ACK\1]
    SHIFTOUT DPIN,CPIN,1,[ADDR_HB]
    SHIFTIN DPIN,CPIN,0,[ACK\1]
    SHIFTOUT DPIN,CPIN,1,[ADDR_LB]
    SHIFTIN DPIN,CPIN,0,[ACK\1]
    GOSUB START_ROM
    SHIFTOUT DPIN,CPIN,1,[CONT1]
    SHIFTIN DPIN,CPIN,0,[ACK\1]
    SHIFTIN DPIN,CPIN,0,[DATI\8]
    SHIFTOUT DPIN,CPIN,1,[%1\1]
    GOSUB STOP_ROM
    PAUSE 10
    RETURN
    
    START_ROM:
    HIGH CPIN:HIGH DPIN:LOW DPIN:RETURN
    STOP_ROM:
    HIGH CPIN:LOW DPIN:HIGH DPIN:RETURN

Make sure you have ANALOG turned off!!

[wolwil]

Thanks for the code guys! I will try it out on sunday when I get back.

[wolwil]

Well I was able to get your code to work. I noticed when I was reading before using the I2CREAD I was getting all 255's and now I am reading using your code and still getting all 255's where ther is no data written so that is telling me that I was getting the I2CREAD to work before. I am now reading through all memory locations looking for the data I wrote to it before using the I2CWRITE command to try and figure out where it wrote it and why. Once this finishes I will post my findings and thoughts.

Thanks again for the code.

PS:
I have not tried Dave's code yet

UPDATE:
I found the written data from my old code in Block 1 of the EEPROM. I am going to go back to the old code I had and try and make it work. I will post my findings

[wolwil]

First and foremost Thank You, Thank You, Thank You for all of your help guys I really do appreciate it.

Here is the working Code:

' Define serial output pin
SO      con     0 

' Define serial mode                          
T2400   con     0                           

' 2 Byte Address Vars
addr1   var     word                       
addr2   var     word                       
addr3   var     word                        

' Vars for data being written
D1      Var     Byte                        
D2      Var     Byte                      
D3      Var     Byte                        

' Vars for data being read
B1      VAR     BYTE                       
B2      VAR     BYTE                       
B3      VAR     BYTE                        

' Set Data Bytes
D1 = 7                                      
D2 = 6
D3 = 5

' Set Address Bytes
addr1 = 1
addr2 = 2
addr3 = 3

I2CWRITE PORTB.1,PORTB.4,$A0,addr1,[D1]      ' Write a 1 to address 1
PAUSE 10                                     ' Wait 10ms for write to complete
I2CWRITE PORTB.1,PORTB.4,$A0,addr2,[D2]      ' Write a 2 to address 2
PAUSE 10                                     ' Wait 10ms for write to complete
I2CWRITE PORTB.1,PORTB.4,$A0,addr3,[D3]      ' Write a 3 to address 3
PAUSE 10                                     ' Wait 10ms for write to complete

I2CREAD PORTB.1,PORTB.4,$A0,addr1,[B1]      ' Read address 1 into B1
I2CREAD PORTB.1,PORTB.4,$A0,addr2,[B2]      ' Read address 2 into B2
I2CREAD PORTB.1,PORTB.4,$A0,addr3,[B3]      ' Read address 3 into B3

Serout SO,T2400,["Addr",#addr1,":",#B1," and then Addr",#addr2,":",#B2," and then Addr",#addr3,":",#B3,13,10] ' Print B1's Value in DEC

and it's out putting this to Hyperterm:

Addr1:7 and then Addr2:6 and then Addr3:5
Addr1:7 and then Addr2:6 and then Addr3:5
Addr1:7 and then Addr2:6 and then Addr3:5

The problem I had in the beginning was I had the SDA/SCL Pins wrong and I did not have the A2 pin Tied to +5V but after correcting those I had my control byte misunderstood and thats why it would not work. After changing the control byte back to $A0 with the A2 held High and the propper pins chosen for SDA and SCL it now works like it should.

I hope this thread saves everyone a ton of time in the future with these chips I know I sure learned a ton from this little experiance