;-----------------------------------------------------------------------------
;
BITIN
MOVLW B'10111111' ; Force SDA line as input
TRIS RB
BSF RB,SDA ; Set SDA for input
BCF EEPROM,DI
BSF RB,SCL ; Clock high
MOVLW 1
BTFSC RB,SCL ; Skip if SCL is high
GOTO BIT1
BTFSS FLAG,ERR1 ; Remain as first error encountered
MOVWF ERCODE ; Save error code
BSF FLAG,ERR1 ; Set error flag
BIT1
BTFSC RB,SDA ; Read SDA PIN
BSF EEPROM,DI ; DI = 1
NOP ; Delay
BCF RB,SCL ; Return SCL to low
RETLW 0
;
;END SUB
PAGE
;
;-----------------------------------------------------------------------------
; Serial data receive from serial EEPROM to PIC, bit-by-bit subroutine
;-----------------------------------------------------------------------------
; Input : EEPROM file
; Output : From (DO) of serial EEPROM device to PIC
;-----------------------------------------------------------------------------
;
BITOUT
MOVLW B'00111111' ; Set SDA, SCL as outputs
TRIS RB
BTFSS EEPROM,DO
GOTO BIT0
BSF RB,SDA ; Output bit 0
MOVLW 2
BTFSC RB,SDA ; Check for error code 2
GOTO CLK1
BTFSS FLAG,ERR1 ; Remain as first error encountered
MOVWF ERCODE ; Save error code
BSF FLAG,ERR1 ; Set error flag
GOTO CLK1 ; SDA locked low by device
;
BIT0
BCF RB,SDA ; Output bit 0
NOP ; Delay
NOP
NOP
CLK1
BSF RB,SCL
MOVLW 1 ; Error code 1
BTFSC RB,SCL ; SCL locked low?
GOTO BIT2 ; No.
BTFSS FLAG,ERR1 ; Yes.
MOVWF ERCODE ; Save error code
BSF FLAG,ERR1 ; Set error flag
BIT2
NOP
NOP
BCF RB,SCL ; Return SCL to low
RETLW 0
;
;END SUB
PAGE
;
;
;-----------------------------------------------------------------------------
; RECEIVE DATA subroutine
;-----------------------------------------------------------------------------
; Input : None
; Output : RXBUF = Receive 8-bit data
;-----------------------------------------------------------------------------
;
RX
MOVLW .8 ; 8 bits of data
MOVWF COUNT
CLRF RXBUF
;
RXLP
RLF RXBUF, F ; Shift data to buffer
SKPC
BCF RXBUF,0 ; carry ---> f(0)
SKPNC
BSF RXBUF,0
CALL BITIN
BTFSC EEPROM,DI
BSF RXBUF,0 ; Input bit =1
DECFSZ COUNT, F ; 8 bits?
GOTO RXLP
BSF EEPROM,DO ; Set acknowledge bit = 1
CALL BITOUT ; to STOP further input
RETLW 0
;
;END SUB
;
;-----------------------------------------------------------------------------
; TRANSMIT DATA subroutine
;-----------------------------------------------------------------------------
; Input : TXBUF
; Output : Data X'mitted to EEPROM device
;-----------------------------------------------------------------------------
;
TX
MOVLW .8
MOVWF COUNT
;
TXLP
BCF EEPROM,DO ; Shift data bit out.
BTFSC TXBUF,7 ; If shifted bit = 0, data bit = 0
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本文关键字：程序 PIC单片机，单片机-工控设备 - PIC单片机
