2019年12月11日 | PIC单片机的IIC接口程序

PIC单片机的IIC接口程序

IniTI2CBusMaster

;************************************************************TxmtStartBit   bsf    Bus_Busy                       ; on a start condiTIon bus is busy   bsf    STATUS, RP0                    ; Select page 1   bsf    _SDA                           ; set SDA high   bsf    _SCL                           ; clock is high   call   Delay40uSec                    ; This is necessary for setup TIme   bcf    _SDA                           ; This gives a falling edge on SDA while clock is high   call   Delay47uSec                    ; Necessary for START HOLD TIme   return;************************************************************TxmtStopBit   bsf    STATUS, RP0                    ; Select page 1   bcf    _SCL                           ; clock is low   bcf    _SDA                           ; set SDA low   bsf    _SCL                           ; clock is pulled up   call   Delay40uSec                    ; Setup time for STOP condition   bsf    _SDA                           ; rising edge on SDA while CLOCK is high   call   Delay47uSec                    ; makes sure a START isn't sent immediately after a STOP   bcf    Bus_Busy                       ; The bus isn't busy anymore   return;************************************************************AbortI2C   call   TxmtStopBit                    ; Send a stop bit   bsf    Abort                          ; set the abort bit   return;************************************************************TxmtSlaveAddr   movf   SlaveAddr, w                   ; Move slave address to W   bcf    ACK_Error                      ; reset Acknowledge error bit   movwf  I2CData                        ; move W to I2C Data   bcf    I2CData, LSB                   ; Set for write   btfsc  Slave_RW                       ; If skip then write operation   bsf    I2CData, LSB                   ; Clear for read   call   SendData                       ; send the address   btfss  Txmt_Success                   ; skip if successful   goto   AddrSendFail                   ; Oops, we failed   retlw  TRUE                           ; return trueAddrSendFail   btfss  ACK_Error                      ; was there an error acknowledging   retlw  FALSE                          ; No, so return 0   call   TxmtStopBit                    ; Address not acknowleged, so send STOP bit   retlw  FALSE                          ; Unsuccessful, so return 0

;************************************************************SendData ; We might should make a copy of the data here, the example does but I don't see why!!!   bsf    Txmt_Progress                  ; We are in the middle of transmitting   bcf    Txmt_Success                   ; reset success bit   movlw  0x08   movwf  I2CBitCount                    ; Set I2C Bit Count to 8   bsf    STATUS, RP0                    ; Select page 1TxmtNextBit:   bcf    _SCL                           ; Set clock Low   rlf    I2CData, F                     ; MSB First, Note that I2CData is Destroyed   bcf    _SDA                           ; Set clock based on what the MSB is   btfsc  STATUS,C                       ; Was the MSB a 1   bsf    _SDA                           ; Nope set it high   call   Delay47uSec                    ; guarantee min LOW TIME tLOW & Setup time   bsf    _SCL                           ; set clock high   call   Delay40uSec                    ; guarantee min HIGH TIME tHIGH   decfsz I2CBitCount, F                 ; are we done yet   goto   TxmtNextBit                    ; nope, send the next bit;; Check For Acknowledge;   bcf    _SCL                           ; reset clock   bsf    _SDA                           ; Release SDA line for Slave to pull down   call   Delay47uSec                    ; guarantee min LOW TIME tLOW & Setup time   bsf    _SCL                           ; clock for slave to ACK   call   Delay40uSec                    ; guarantee min HIGH TIME tHIGH   bcf    STATUS, RP0                    ; Select PAGE 0 to test SDA pin   btfsc  SdaPin                         ; SDA should be pulled low by slave if OK   goto   TxmtErrorAck                   ; Uh oh, slave isn't behaving (or isn't there)   bsf    STATUS, RP0                    ; Select PAGE 1   bcf    _SCL                           ; reset clock   bcf    Txmt_Progress                  ; reset progress bit in Bus Status   bsf    Txmt_Success                   ; Transmission successful   bcf    ACK_Error                      ; ACK OK   returnTxmtErrorAck   bsf    STATUS,RP0                     ; select page 1   bsf    _SDA                           ; tristate SDA   bsf    _SCL                           ; tristate SCL   bcf    Txmt_Progress                  ; reset progress bit in Bus Status   bcf    Txmt_Success                   ; Transmission NOT successful   bsf    ACK_Error                      ; No ACK From Slave   return