Example program for reading and writing EEPROM of 24LCxx series

;************************************************* *******
;* *
;*? PIC16F877A ?I2C Master Home Î‘???ï¹ƒ?Î‘ EEPROM? ç»¦ã„’ç¥˜Î‘ *
;* *
;* Written by: Richard Yang *
;* Sr. Corporate ApplicaTIon Engineer *
;* Microchip Technology Inc. *
;* Date: Oct. 2nd '2002 *
;* Revision: 1.00 *
;************************************************* *******

;*************************************************
; This source code provides a demonstraTIon of the MSSP peripheral
; on the PIC16F87x MCU.
;
;
;*********** The subrouTInes for EEPROM *****************
;
; EE_Random_Read; EEPROM Random address Read from EEPROM
; EE_SEQU_Read; EEPROM SequenTIal Read form EEPROM
; EE_Ack_Check; Polling current status of EEPROM
; EE_Page_Write; Page Write function for EEPROM
; EE_Byte_Write; Write a byte to EEPROM with address setting
;
;*********** The subroutines for I2C *****************
;
; Init_I2C_Master; Initial I2C Module for Master Mode, 7-bit address
; StartI2C; Send a START Condition !!
; StopI2C; Send s STOP Condition
; RstartI2C; Send a Repeat Start conditional to I2C
; Non_Ack; Send a Non-acknowledge signal to I2C
; An_Ack; Send a acknowledge signal to I2C
; Sebd_Byte; Send a byte to I2C bus
; RecI2C; Enable Read a byte form slave device
; I2C_Done: Wait the I2C completed the currect process
;
;************************************************* **

list p=16f877a
#I nclude

;
;***************************************
; ï¹šç«¡è·‘è®¡?RAM???
;
CBLOCK 0x20

I2C_Ctrl
I2C_Addr
I2C_Data
I2C_Page_Length
D_Count
ENDC
cblock 0x40
I2C_Page_Buffer:8
I2C_SEQU_Buffer:8
endc
;
;***************************************
; ï¹šç«¡ã„è€ž? Both? Actually??

w_temp EQU 0x72
status_temp EQU 0x73
pclath_temp EQU 0x74
;
;***************************************
; ï¹šç«¡I2C ???ã®ç«²?
;
EEPROM_CMD equ 0xA0; Device adress of Slave Point
EE_Read equ .1
EE_Write equ .0

;
#define SCL PORTC,3; I2C SCL pin
#define SDA PORTC,4; I2C SDA pin

;

;********************************************
; Locates startup code @ the reset vector
;********************************************
Reset_Addr
org 0x00
nop
goto Main_Init
;
org 0x04
goto ISR
;
;************************************************* ************
;**** The Start Address of ISR is 0x004
;**** "PUSH" & "POP" ?ã„ãƒŽç»¦ã„’: ç¶šãƒŽ?å‹¾PIC16F877 Î¤SHARE BANK ?PIC
;************************************************* *************
ISR
Push movwf w_temp; save off current W register contents
movf STATUS,w; move status register into W register
movwf status_temp; save off contents of STATUS register
movf PCLATH,W
movwf pclath_temp
;
; Put your interrupt code here
;
Pop movf pclath_temp,W
movwf PCLATH
movf status_temp,w; retrieve copy of STATUS register
movwf STATUS; restore pre-isr STATUS register contents
swapf w_temp,f
swapf w_temp,w; restore pre-isr W register contents
;
retfie; return from interrupt

;------------------------------------------------- ---------------------

Main_Init
pagesel Init_I2C_Master; Set PAGE to PCLATH Register
call Init_I2C_Master; Init the MSSP for I2C Master
;
banksel I2C_Ctrl
movlw EEPROM_CMD; Load EEPROM command address @ 0xA0
movwf I2C_Ctrl
;
;
Main
;
;------------------------------------------------- ---------------------
;
;* ???????????????????????????????????????????????????????????? RMA0x40-0x47?????
;* ?ãƒŽPage Write?ã‚ˆÎ‘ç›¢8??ã˜æ©Ÿ?Ge?ç²œ? EEPROM?
;* ç±¼ï¸½?ç¯ˆ? Ang-generation EEPROM çŒ??Ð§Î˜ç²œ??bar?? Cheng?ç›¢?ç²œ
;* ??Ge??Sequential Read?ã‚ˆÎ‘çœ–EEPROMGet?ã„“??I2C_SEQU_Bufferã„
;

Test_Page_RW
movlw 0x08
movwf I2C_Page_Length
movlw I2C_Page_Buffer
_Fill_RAM movwf FSR
movwf INDF
incf FSR,W
decfsz I2C_Page_Length,F
goto _Fill_RAM
;
Test_Page_Write
; banksel I2C_Ctrl
movlw EEPROM_CMD; Load EEPROM command address @ 0xA0
movwf I2C_Ctrl
movlw 0x10; Select EEPROM location at 0x00
movwf I2C_Addr
movlw .8
movwf I2C_Page_Length
call EE_Page_Write
;
call EE_Ack_Check
;
banksel I2C_Ctrl
movlw EEPROM_CMD; Load EEPROM command address @ 0xA0
movwf I2C_Ctrl
movlw 0x10
movwf I2C_Addr
movlw .8
movwf I2C_Page_Length
call EE_SEQU_Read
;
goto $
;
;------------------------------------------------- --------
;
;* ???ä»£åˆšç¥˜Î‘ç©¦?ç²œ???? ã˜æ©Ÿ?æˆˆ?ç²œ? EEPROM ã„
;* ?ç±¼ï¸½?ç¯ˆ? AngdaiçŒ??Ð§Î˜ç²œ??bar?? Cheng?ç›¢?ç²œ
;* ??Ge?? EEPROM get? ã„“?? I2C_Data å„ªæœ–çœ–ã„
;
Test_1byte_RW

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

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