PIC单片机的IIC接口程序

PIC单片机的IIC接口程序

;************************************************************GetData   bsf    Rcv_Progress                   ; set Bus status for txmt progress   bcf    Rcv_Success                    ; reset status bit   movlw  0x08   movwf  I2CBitCountRcvNextBit   bsf    STATUS, RP0                    ; page 1 for TRIS manipulation   bcf    _SCL                           ; lower clock   bcf    _SDA                           ; lower data line   call   Delay47uSec                    ; guarantee min LOW TIME tLOW & setup time   bsf    _SCL                           ; clock high, data sent by slave   call   Delay40uSec                    ; guarantee min HIGH TIME tHIGH   bcf    STATUS, RP0                    ; select page 0 to read Ports   bcf    STATUS, C                      ; 0 out Status   btfsc  SdaPin                         ; Check state of pin   bsf    STATUS, C                      ; Pin was high, set status   rlf    I2CData, F                     ; left Shift data (MSB first)   decfsz I2CBitCount, F                 ; Are we done yet   goto   RcvNextBit                     ; Nope, go get the next one;; Generate ACK bit if not last byte to be read,; if last byte Gennerate NACK ; do not send ACK on last byte, main routine will send a STOP bit;   bsf    STATUS, RP0                    ; Page 1 for TRIS manipulation   bcf    _SCL                           ; pull SCL low   bcf    _SDA                           ; ACK by pulling SDA low   btfsc  Last_Byte_Rcv                  ; Is it the last byte to receive   bsf    _SDA                           ; If so, send NACK by setting SDA high   call   Delay47uSec                    ; guarantee min LOW TIME tLOW & Setup time   bsf    _SCL                           ; Raise Clock back up   call   Delay40uSec                    ; guarantee min HIGH TIME tHIGHRcvEnd:   bcf    _SCL                           ; reset clock   bcf    Rcv_Progress                   ; reset bit in Bus Status   bsf    Rcv_Success                    ; transmission successful   bcf    ACK_Error                      ; ACK OK   return

Delay47uSec:   movlw ((_47uS_Delay-5)/3 + 1)         ; move delay into WDlyK   movwf DelayCount                      ; move what is in W to DelayCount   decfsz   DelayCount, F                ; Decrement DelayCount   goto  $-1                             ; Loop until 0   return                                ; return

Delay40uSec:   movlw ((_40uS_Delay-8)/3 + 1)         ; move delay into W   goto  DlyK                            ; goto DlyK loop

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