使用PIC读写1-wire EEPROM DS2430的实例

  movwf Addr
  movlw H'35' 
  banksel TxBuffer
  movwf TxBuffer
  call WrDS2430 
 
  movlw H'02'
  banksel Addr
  movwf Addr
  movlw H'36'
  banksel TxBuffer
  movwf TxBuffer
  call WrDS2430 
 
   
;-------- read address 0 -------------------------- 
  movlw H'00'
  movwf Addr
  call RdDS2430
 
  goto $   
;----------------------------------------------
; template to init before write
; to DS2430
;----------------------------------------------- 
;  movlw H'00'
;  movwf Addr 
;  movlw H'3C'
;  movwf TxBuffer 
 
;---------------------------------------------
; write DS2430 one byte
; input
; Addr = starting address to write
; TxB  = data to save
; output =
; ErrCode = 0 -> write ok
;  = 1 -> write fail
;-----------------------------------------------
WrDS2430 
  call WrScratchPAD
  call CP2EE
  return

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;------------------------------------------------
; template to init before read
; to DS2430
;------------------------------------------------- 
;   movlw H'00'
;  movwf Addr  

;-------------------------------------------------
; read DS2430 one byte
; input
; Addr = starting address to read
; output
; RxB  = data to read
;--------------------------------------------------
RdDS2430
  call REE2ScratchPAD 
  call HostRdScratchPAD
  return

;;---------  host read scratch pad ----------------------------
;; save desired data into RxB
;;
;;--------------------------------------------------------------
 
HostRdScratchPAD
  call  DS2430AInitState
  banksel TxB
  movlw SkipROM
  movwf TxB 
  call  TxBYTE    ; SkipROM
 
  movlw RScratch   ; read scratch PAD Command
  movwf TxB
  call TxBYTE
 
  movf Addr,W    ; starting address to read
  movwf TxB
  call TxBYTE
   
  call R2430A    ; read desired scratch pad into RxB
  call    RstPulse
  return
 
 
;-------------- write memory scratch scratch pad ------------------------
; write one byte into scratch PAD
; input
; Addr   = starting address to write
; TxBuffer = data to save
; output
; ErrCode = 0 -> write ok
;   = 1 -> write fail
;---------------------------------------------------------------------------

WrScratchPAD
  call DS2430AInitState
  movlw SkipROM    ; 0xCC
  movwf TxB
  call  TxBYTE    ; SkipROM
 
  movlw WScratch   ; write memory scratch pad, 0x0f
  movwf TxB
  call TxBYTE
 
  movf Addr,W    ; starting address of memory scratch pad
  movwf TxB     ; TxBYTE use TxB
  call TxBYTE
 
  movf TxBuffer,W   ;
  movwf TxB
  call TxBYTE   
  call RstPulse   ; reset pulse
  call delay500us   ; wait presence pulse   
  return 
 
;---------- CP2EE ---copy whole scratch pad to EE ----------------------
;  write memory scratch
;  verify memory scratch
;  copy memory scratch to EE
;----------------------------------------------------------------------
CP2EE
  call  DS2430AInitState ; 0x55 + 0xa5 + hi 10ms // [ScratchPad -> EEPROM ] 
  banksel TxB
  movlw SkipROM
  movwf TxB 
  call  TxBYTE    ; SkipROM
  movlw CPScratch   ; 0x55
  movwf TxB
  call TxBYTE
  movlw H'a5'
  movwf TxB
  call TxBYTE
  call ForceHi    ; min 10ms refter to datasheet
  return

;--------- REE2ScratchPAD --- copy whole EE to ScrathPAD ----------------
;  copy EE to whole memory scatch
;  read memory scratch
;format I:  0xf0 + Addr +R +R + reset pulse, copy byte by byte
;format II:  0xf0 + Addr + reset pulse, copy whole
;------------------------------------------------------------------------
REE2ScratchPAD
  call  DS2430AInitState
  banksel TxB
  movlw SkipROM
  movwf TxB 
  call  TxBYTE    ; SkipROM
  movlw REEROM    ;; Read from EE into ScratchPAD
  movwf TxB
  call TxBYTE    ;;
  call    RstPulse   ;; copy all
  return
 
;----------R2430A ---- Host read the scratch PAD ------------------------
; Read 2430A Scratch PAD
; LSB first
;   save the result in RxB
;------------------------------------------------------------------------

R2430A               ; returns byte in RxB
  movlw .8
  movwf LoopCounter
        clrf RxB
RLoop
  call  SetLo   ;
        nop
  call  SetHi   ; it will pull up by resistor
  nop      ; delay to sample reliable bit
  nop
  nop
  nop
  nop
  nop
  nop
  nop
  nop
  nop
  nop 
        nop
        nop
        nop
        nop
       
        banksel PORTB
        movf PORTB,W
        movwf Temp
        btfss Temp,Bit2

  goto gLo
  bsf  CARRY
  goto rol
gLo 
  bcf  CARRY
rol 
  banksel RxB
        rrf  RxB,F
        call delay60us  ; tdrv + trelease
        banksel LoopCounter
        decfsz LoopCounter,F
        goto RLoop
        movf RxB,W   ; save the result in W
        return
  
;----------------------------------------------------------
; strong pull up
;
;----------------------------------------------------------
ForceHi

  bsf  PBDir,Bit2
  movf PBDir,W   ;; input

  banksel TRISB
  movwf TRISB   ;; set input, pull by external resistor
  call delay100ms
  bcf  PBDir,Bit2  ;; output
  movf PBDir,W
  movwf TRISB
        return

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