24LCxx系列的EEPROM的读写程序实例

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 call EE_Ack_Check ; Polling Acknowledge for next access
;
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+ 0xA0 + EE_Address + ReStart + 0xA1 + Read_Data + NAck + Stop
;

EE_Random_Read
call StartI2C ; 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 RstartI2C ; Send a Repeat Start 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 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+ 0xA0 + EE_Address + ReStart + 0xA1 + Read_Data + NAck + Stop
;
EE_SEQU_Read
call StartI2C ; 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 RstartI2C ; Send a Repeat Start 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 loop check
;*
;******************************************************
;
EE_Ack_Check
call StartI2C ; 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 RstartI2C ; Send a Repeat Start 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+ 0xA0 + EE_Address + W_Data 0+ .. + W_Data N + Stop
;
EE_Page_Write
movf I2C_Page_Length,W
btfsc STATUS,Z
return
;
call StartI2C ; 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+ 0xA0 + EE_Address + Write_Data + Stop
;
EE_Byte_Write
call StartI2C ; 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
;
;**********************************************************************
;
;*** 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 condition to bus *******
;
StartI2C ; Initiate the I2C START 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 condition to bus *******
;
RstartI2C
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