读写24LCxx系列的EEPROM的实例程序

   banksel I2C_Ctrl
   movlw EEPROM_CMD   ; Load EEPROM command address @ 0xA0
   movwf I2C_Ctrl
   movlw 0x00    ; Select EEPROM location at 0x00
   movwf I2C_Addr
   movlw 0xAA    ; Write data 0x5A to location 0x00 of EEPROM
   movwf I2C_Data
   call EE_Byte_Write
;
Test2(＄0.3696)  call EE_Ack_Check  ; Polling Acknowledge for next access(＄49.9920)
;
   banksel I2C_Data
   movlw 0x00    ; Clear I2C data buffer
   movwf I2C_Data
;
Test3
   banksel I2C_Ctrl
   movlw EEPROM_CMD   ; Load EEPROM command address @ 0xA0
   movwf I2C_Ctrl
   movlw 0x00
   movwf I2C_Addr
   call EE_Random_Read
   ;
   goto  $
;

;
;******************************************************
;*           Random Read a Byte from EEPROM         
;*
;* Input:
;*     - I2C_Ctrl : Control Byte of EEPROM   
;*      - I2C_Addr : Location of EEPROM  
;* Output:
;*      - I2C_Data : Read Data from EEPROM   
;******************************************************
;
; Send Command for RANDOM READ :
; " START(＄0.5760)+ 0xA0 + EE_Address + ReSTART(＄0.5760) + 0xA1 + Read_Data + NAck + Stop "
;

EE_Random_Read
    call START(＄0.5760)I2C  ; Set SSPCON2.SEN
;
   bcf  I2C_Ctrl,0  ; set for write Command
   movf I2C_Ctrl,W  ; Send Slave Address to I2C Bus
   call Send_Byte
;
   movf I2C_Addr,W  ; Send out the Rendom address of EEPROM 
   call Send_Byte
;
   call RSTART(＄0.5760)I2C  ; Send a Repeat START(＄0.5760) to I2C
;
   bsf  I2C_Ctrl,0  ; set for Read Command
   movf I2C_Ctrl,W  ; Send Slave Address to I2C Bus
   call Send_Byte
;
   call RecI2C  ; Enable I2C Receive
;
   BANKSEL SSPBUF
   movf SSPBUF,W ; Save to I2C_Data First !!
   movwf I2C_Data

   call Non_Ack  ; Initial NACK Response !!

   call StopI2C  ; Initial STOP Condition
   return
;
;***************************************************************
;*                Sequential Read from EEPROM         
;*
;* Input:
;*     - I2C_Ctrl : Control Byte of EEPROM   
;*      - I2C_Addr : START(＄0.5760) Location of EEPROM
;*     - I2C_Page_Length : How many byte need to read  
;* Output:
;*      - I2C_SEQU_Buffer : Sequential Read Data buffer
;*  
;***************************************************************
;
; Send Command for RANDOM READ :
; " START(＄0.5760)+ 0xA0 + EE_Address + ReSTART(＄0.5760) + 0xA1 + Read_Data + NAck + Stop "
;
EE_SEQU_Read
    call START(＄0.5760)I2C  ; Set SSPCON2.SEN
;
   bcf  I2C_Ctrl,0  ; set for write Command
   movf I2C_Ctrl,W  ; Send Slave Address to I2C Bus
   call Send_Byte
;
   movf I2C_Addr,W  ; Send out the Rendom address of EEPROM 
   call Send_Byte
;
   call RSTART(＄0.5760)I2C  ; Send a Repeat START(＄0.5760) to I2C
;
   bsf  I2C_Ctrl,0  ; set for Read Command
   movf I2C_Ctrl,W  ; Send Slave Address to I2C Bus
   call Send_Byte
;
   movlw I2C_SEQU_Buffer
   movwf FSR
;
_Sequ_Loop call RecI2C   ; Enable I2C Receive
   BANKSEL SSPBUF
   movf SSPBUF,W  ; Save to I2C_Data First !!
   movwf INDF
   incf FSR,F
   decfsz I2C_Page_Length,F
   goto _Cont_Read
   goto _End_Read
_Cont_Read call An_Ack
   goto _Sequ_Loop
;
_End_Read call Non_Ack   ; Initial NACK Response !!
   call StopI2C   ; Initial STOP Condition
   return
;
;******************************************************
;*              EEPROM Acknowledge Polling
;*           
;*     --  The routine will polling the ACK  
;*           response from EEPROM       
;*    --  ACK=0 return        
;*   --  ACK=1 send ReSTART(＄0.5760) & loop check
;* 
;******************************************************
;
EE_Ack_Check
    call START(＄0.5760)I2C  ; Set SSPCON2.SEN
   
   bcf  I2C_Ctrl,0  ; Clear for Write Command
   movf I2C_Ctrl,W  ; Send Slave Address to I2C Bus
   call Send_Byte
_Ack_Polling
   BANKSEL SSPCON2
   btfss SSPCON2,ACKSTAT ; Check ACKSTAT bit , 0 = ACK , 1 = NACK
   goto ACK_Return  ; Ack = 0 ; EEPROM is Ready
_Ack_Hi        ; Ack = 1 ; EEPROM is Busy for Write
   call Delay_mS  ; Delay 500uS for next Ack polling
   call RSTART(＄0.5760)I2C  ; Send a Repeat START(＄0.5760) to I2C
   bcf  I2C_Ctrl,0  ; Clear for Write Command
   movf I2C_Ctrl,W  ; Send Slave Address to I2C Bus
   call Send_Byte
   goto _Ack_Polling
 
ACK_Return
   call StopI2C   ; Initial STOP Condition
   return
;
;**********************************************************
;*           Page Write 1 to 8 Bytes to EEPROM        
;*
;*  Input:
;*     - I2C_Ctrl : Control Byte of EEPROM  
;*     - I2C_Addr : Location of EEPROM  
;*   - I2C_Page_Buffer: RAM location of Data
;*     - I2C_Page_Length : Data length count
;*  
;**********************************************************
;
; Send Command for PAGE WRITE :
; " START(＄0.5760)+ 0xA0 + EE_Address + W_Data 0+ .. + W_Data N + Stop "
;
EE_Page_Write
   movf I2C_Page_Length,W
   btfsc STATUS,Z
   return
;  
    call START(＄0.5760)I2C  ; Set SSPCON2.SEN
;
   bcf  I2C_Ctrl,0  ; Clear for Write Command
   movf I2C_Ctrl,W  ; Send Slave Address to I2C Bus
   call Send_Byte
;
   movf I2C_Addr,W  ; Send out the Command 
   call Send_Byte
;
   movlw I2C_Page_Buffer
   movwf FSR
_W1   movf INDF,W
   call Send_Byte
   incf FSR,F
   decfsz I2C_Page_Length,F
   goto _W1
;
    call StopI2C   ; Initial STOP Condition
   return
;
;
;*******************************************************
;*               Write a Byte to EEPROM               
;*
;* Input:
;*     - I2C_Ctrl : Control Byte of EEPROM   
;*      - I2C_Addr : Location of EEPROM  
;*      - I2C_Data : Data to EEPROM
;*  
;*******************************************************
;
; Send Command for BYTE WRITE :
; " START(＄0.5760)+ 0xA0 + EE_Address + Write_Data + Stop "
;
EE_Byte_Write
    call START(＄0.5760)I2C  ; Set SSPCON2.SEN
;
   bcf  I2C_Ctrl,0  ; Clear for Write Command
   movf I2C_Ctrl,W  ; Send Slave Address to I2C Bus
   call Send_Byte
;
   movf I2C_Addr,W  ; Send out the Command 
   call Send_Byte
;
   movf I2C_Data,W  ; Send out the Data
   call Send_Byte
;
    call StopI2C   ; Initial STOP Condition
   return
;
;**********************************************************************
;
;   As following subroutines perform commonly used I2C functions.
;      You can use these subroutines for your I2C access(＄49.9920)
;
;**********************************************************************
;
;*** Initial I2Cmodule fot 7-bit I2C Master Mode with 100Kcps @4MHz
;
Init_I2C_Master    
   BANKSEL TRISC   ; Initial PortC,bit 3 & 4 as Input
    bsf  SCL    ; RC3 = SCL  ,  RC4 = SDA
   bsf  SDA  
;
    BANKSEL PORTC
    bsf  SCL    ; SCL = Hi
    bsf  SDA    ; SDA = Hi
;
   movlw b'00101000'  ; I2C Master Mode, Clock Rate: FOSC/(4*SSPADD+1)
   movwf SSPCON   ;
;
         banksel SSPADD
         movlw   .9              ; This gives 100KHz I2C clock @ 4MHz
   movwf   SSPADD   ; (4MHz/4) / (9+1)= 100KHz
;
       movlw   b'10000000'     ; Disable slew rate control,
         movwf   SSPSTAT   ; and clear status bits
;
          movlw   b'00000000'     ; Set SCL,SDA into Ready status
         movwf   SSPCON2         
;    
   return
;
;******   Send START(＄0.5760) condition to bus   *******
;
START(＄0.5760)I2C    ; Initiate the I2C START(＄0.5760) condition.
         banksel SSPCON2
          bsf     SSPCON2,SEN
         goto I2C_Done
;
;******   Send STOP condition to bus   *******
;
StopI2C    
        banksel SSPCON2
         bsf     SSPCON2,PEN
         goto I2C_Done
;
;******   Send RESTART(＄0.5760) condition to bus   *******
;     
RSTART(＄0.5760)I2C   
         banksel SSPCON2
         bsf     SSPCON2,RSEN
         goto I2C_Done
;
;******   Send a Non-Acknowledge status to bus (ACK=1)    *******
;       
Non_Ack
         banksel SSPCON2
         bsf     SSPCON2,ACKDT    ; Set the ACK bit
         bsf     SSPCON2,ACKEN    ; Initiate the NACK sequence.
         goto I2C_Done
;
;******   Send an Acknowledge status to bus (ACK=0)     *******
;        
An_Ack
          banksel SSPCON2
         bcf     SSPCON2,ACKDT    ; Clear the ACK bit
         bsf     SSPCON2,ACKEN    ; Initiate the NACK sequence.
         goto I2C_Done
;
;******   Send data to I2C bus from Wreg.     *******
;
Send_Byte
   banksel SSPBUF
   movwf SSPBUF
   goto I2C_Done
;
;******   Enable I2C Receive for Master Mode     *******
;
RecI2C
        banksel SSPCON2         
         bsf     SSPCON2,RCEN    ; Set the receive enable bit.
   goto I2C_Done
;
;******  Check the I2C stage is completed   ********
;
I2C_Done
         banksel PIR1
    btfss   PIR1,SSPIF ; Poll for SSPIF
         goto    $-1
         bcf     PIR1,SSPIF
         return
;
Delay_mS
   banksel D_Count
   movlw .124   ; Load .5mS Dealy Value
    movwf D_Count   
_D_mS  nop
   decfsz D_Count,F  
   goto _D_mS 
   return         
;
; *********** End Of Program !!!!!
;
   end