Enter with bank 0 selected. Underscored are bit names, here mostly from SSPCON2.
SELRP0 = BCF STATUS,RP0 SELRP1 = BSF STATUS,RP0 LDB REG,DATA = MOVLW DATA, MOVWF REG ; ------------------------------ ; I2C INIT SEQUENCE ; ------------------------------ LDB SSPCON,B'00101000' ;I2C MASTER SELRP1 LDB SSPSTAT,B'10000000' ;NO SLEW RATE CONTROL LDB SSPCON2,B'01100000' LDB SSPADD,D'10' ;ADJUST ACCORDING TO CLOCK & I2C SPEED SELRP0 RETURN ; ------------------------------ ; ISSUE I2C START CONDITION ; ------------------------------ I2CST: SELRP1 BSF _SEN BTFSC _SEN GOTO $-1 SELRP0 RETURN ; -------------------------------- ; ISSUE I2C REPEAT START CONDITION ; -------------------------------- I2CRST: SELRP1 BSF _RSEN BTFSC _RSEN GOTO $-1 SELRP0 RETURN ; ------------------------------ ; ISSUE I2C STOP CONDITION ; ------------------------------ I2CSP: SELRP1 BSF _PEN BTFSC _PEN GOTO $-1 SELRP0 RETURN ; ------------------------------ ; I2C TRANSMIT DATA ; INPUT W - DATA ; OUTPUT CARRY - ACKNOWLEDGE ; ------------------------------ I2CTX: MOVWF SSPBUF SELRP1 BTFSC _R_W GOTO $-1 BCF _C BTFSC _ACKSTAT BSF _C SELRP0 RETURN ; ------------------------------ ; I2C RECEIVE DATA ; INPUT CARRY - ACKNOWLEDGE ; OUTPUT W - DATA ; ------------------------------ I2CRX: SELRP1 BCF _ACKDT BTFSC _C BSF _ACKDT BSF _RCEN BTFSS _BF GOTO $-1 BSF _ACKEN BTFSC _ACKEN GOTO $-1 SELRP0 MOVF SSPBUF,W RETURN
...the I2C protocol always consists of start, restart, byte read, byte write and stop. Eeproms have several modes of operation - byte write, page write, current address read, random read, continuous read. At this point you have to reffer to the datasheet for applicable modes of operation. Example 24C02 byte write (untested):
; ------------------------------------- ; input _24c02addr - address in eeprom ; input _24c02data - data to be written ; ------------------------------------- _24c02wr: call i2cst ;issue start movlw 0xA0 ;transmit device address call i2ctx ;(all address pins low) btfsc status,carry goto _24c02wr0 ;error - no acknowledge movf _24c02addr,w ;transmit byte address call i2ctx movf _24c02data,w ;transmit data call i2ctx _24c02wr0: call i2csp ;issue stop return
After this, the eeprom will not acknowledge its address until the internal write has finished. It can be used for testing end of write:
_24c02wait: call i2cst movlw 0xA0 ;try to address the eeprom call i2ctx call i2csp ;i2csp preserves carry bit btfsc status,carry goto _24c02wait ;no acknowledge, try again return
Questions: