i2c.asm

使用软件模拟Ｉ２Ｃ与ＥＥＰＲＯＭ通讯的子程序

$NOMOD51       
$include (c8051f330.inc)			 
			 sda   equ   p1.6
       SCK   equ   p1.7
       wp    equ   p1.5
       org   0000h
			 ljmp  main
			 org   0030h


main:    anl  PCA0MD,    #NOT(040h)          ;关闭看门狗
				 MOV  SP,#60H
         MOV  OSCICN,#080H      ;设置时钟频率为3.0625M
         MOV  P0MDOUT,#0FFH
         MOV  P1MDOUT,#03FH
         MOV  P0SKIP,#0FFH
         MOV  P1SKIP,#0FFH
         MOV  XBR1,#040H

 ;   acall  ds1337_ini
    mov    r0,#00H
		mov    dpl,#0Eh
    acall  WR_BYTE
    mov    r0,#00h
    mov    dpl,#0fh
    acall  WR_BYTE

    mov    r0,#4AH       ;存放到一4AH为首地址的连续7个内存单元中。
    mov    dpl,#00h
		mov    r6,#7
    acall  RD_SEN
    sjmp   $


ds1337_ini:    nop
    mov    3ah,#000h     ;second
    mov    3bh,#040h     
    mov    3ch,#015h
    mov    3dh,#002h
		mov    3eh,#025h
		mov    3fh,#007h
    mov    40h,#006h     ;year
    mov    dpl,#00h
		mov    r0,#3ah       ;首地址为3AH
		mov    r6,#7      
    acall  WR_BLK






;	24C02写一个字节
;Input:R0
;---------------------------------------
WR_BYTE:CLR	WP	;允许写EEPROM
	CALL	START		;开始信号
	JC	WRBT2
	MOV	A,#0D0H		; specify write operation
	CALL	SHOUT		;发送控制字
	JC	WRBT1		;从器件不响应，转结束
;	MOV	A,DPH		;设置从器件片内高地址
;	CALL	SHOUT
;	JC	WRBT1		;从器件不响应，转结束
	MOV	A,DPL		;设置从器件片内低地址
	CALL	SHOUT
	JC	WRBT1		;从器件不响应，转结束
	MOV	A,R0		;从R0取数据
	CALL	SHOUT		;发送数据
	JC	WRBT1		;从器件不响应，转结束
	CLR	C		;清错误标志
WRBT1:	CALL	STOP		;停止信号
WRBT2:	SETB	WP		;禁止写EEPROM
	RET
;---------------------------------------
;	24C02块写(WR_BLK)
;入口：待写字节在R0指向的缓冲器中，个数在R6；
;---------------------------------------
WR_BLK:	CLR	WP		;允许写EEPROM
	CALL	START		;开始信号
	JC	WR_BL2
	MOV	A,#0D0H		; specify write operation
	CALL	SHOUT		;发送控制字
	JC	WR_BL1		;从器件不响应，转结束
;	MOV	A,DPH		;设置从器件片内高地址
;	CALL	SHOUT
;	JC	WR_BL1		;从器件不响应，转结束
	MOV	A,DPL		;设置从器件片内低地址
	CALL	SHOUT
	JC	WR_BL1		;从器件不响应，转结束
WR_BL5:	MOV	A,@R0		;从R0取数据
	CALL	SHOUT		;发送数据
	JC	WR_BL1		;从器件不响应，转结束
	inc	R0		; advance buffer pointer
	djnz	R6,WR_BL5	; next byte
	CLR	C		;清错误标志
WR_BL1:	CALL	STOP		;停止信号
WR_BL2:	SETB	WP		;禁止写EEPROM
	RET
;---------------------------------------
;	E2PROM当前地址读取
;---------------------------------------
RD_CUR:	CALL	START		;开始信号
	JC	x45		;从器件不响应，转结束
	MOV	A,#0D1H		; specify read operation
	CALL	SHOUT		;发送控制字
	JC	x44		;从器件不响应，转结束
	CALL	SHIN		;接收数据
	CALL	NAK		;发送确认位（高）
	CLR	C		;清错误标志
x44:	CALL	STOP		;停止信号
x45:	RET
;---------------------------------------
;	E2PROM随机读取
;---------------------------------------
RD_RND:	CALL	START		; Send dummy write command to set internal address.
	JC	x47		; abort if bus not available
	MOV	A,#0D0H		; specify write operation
	CALL	SHOUT		; send device address
	JC	x46		; abort if no ACKKnowledge
;	MOV	A,DPH		; send high byte of address
;	CALL	SHOUT		
;	JC	x46		; abort if no ACKKnowledge
	MOV	A,DPL		; send low byte of address
	CALL	SHOUT		
	JC	x46		; abort if no ACKKnowledge
	CALL	RD_CUR		; Call Current Address Read function.
	JMP	x47		; exit
x46:	CALL	STOP
x47:	RET
;---------------------------------------
;	E2PROM连续读取(RD_SEN)
;入口：R0为缓冲器的首址，要读的个数在R6；
;出口：读出的数据送入R0指向的缓冲器中
;---------------------------------------
RD_SEN:	CALL	START		; Send dummy write command to set internal address.
	JC	RD_S7		; abort if bus not available
	MOV	A,#0D0H		; specify write operation
	CALL	SHOUT		; send device address
	JC	RD_S6		; abort if no ACKKnowledge
;	MOV	A,DPH		; send high byte of address
;	CALL	SHOUT
;	JC	RD_S6		; abort if no ACKKnowledge
	MOV	A,DPL		; send low byte of address
	CALL	SHOUT
	JC	RD_S6		; abort if no ACKKnowledge
	CALL	START		;开始信号
	JC	RD_S7		;从器件不响应，转结束
	MOV	A,#0D1H		; specify read operation
	CALL	SHOUT		;发送控制字
	JC	RD_S6		;从器件不响应，转结束
RD_S1:	CALL	SHIN		;接收数据
	MOV	@R0,A
	cjne	R6,#1,RD_S2	; jump if not last byte
	call	NAK		; do not ACKKnowledge last byte
	jmp	RD_S3		; done
RD_S2:	call	ACKK		; ACKKnowledge byte
	inc	R0		; advance buffer pointer
	djnz	R6,RD_S1	; next byte
RD_S3:	clr	c		; clear error flag
RD_S6:	CALL	STOP
RD_S7:	RET
;---------------------------------------
;	I2C总线控制程序
;---------------------------------------
;开始信号。Send START, defined as high-to-low SDA with SCK high.
;出口：SCK=SDA=低；若总线不可用，CY=高.
;---------------------------------------
START:	CLR	SCK
	NOP
	SETB	SDA
	SETB	SCK
	SETB	C		;错误标志置位
	JNB	SDA,x41		;Verify bus available.
	JNB	SCK,x41		;jump if not high
	CLR	SDA
	NOP			;延时
	NOP	
	CLR	SCK
	CLR	C		;清错误标志
x41:	RET
;---------------------------------------		   	
;停止信号。Send STOP, defined as low-to-high SDA with SCK high.
;入口：SCK=低；出口：ADSCK=SDA=高.
STOP:	CLR	SDA
	NOP			;enforce SCK low and data setup
	NOP
	SETB	SCK
	NOP			;延时
	NOP	
	SETB	SDA
	RET
;---------------------------------------
;移位输出ACC到24LC64，高有效位在前
; SCK, SDA expected low on entry. Return with SCK low.
; Returns CY set to indicate failure by slave to ACKKnowledge.
; Destroys A.
SHOUT:	MOV	R7,#8		;bit counter
SOUT1:	RLC	A		;move bit into CY
	MOV	SDA,C		;output bit
	NOP			;enforce SCK low and data setup
	SETB	SCK		;raise clock
	NOP			;延时
	NOP	
	CLR	SCK		;drop clock
	DJNZ	R7,SOUT1	;next bit
	SETB	SDA		;release SDA for ACKK
	NOP			;延时
	NOP	
	SETB	SCK		;raise ACKK clock
	NOP			;延时
	NOP	
	MOV	C,SDA		;get ACKK bit
	CLR	SCK		;drop ACKK clock
	RET
;---------------------------------------
;移位输入一个字节到ACC。Shift in a byte from the AT24Cxx, most significant bit first.
; SCLK expected low on entry. Return with SCLK low.
; Returns received data byte in A.
SHIN:	;CLR	A
	SETB	SDA		;make SDA an input
	MOV	R7,#8		;bit count
SHIN1:	NOP			;enforce SCK low and data setup
	NOP
	SETB	SCK		;raise clock
	NOP			;延时
	NOP
	MOV	C,SDA		;input bit
	RLC	A		;move bit into byte
	NOP
	CLR	SCK		;drop clock
	DJNZ	R7,SHIN1	;next bit
	RET
;---------------------------------------
;发送确认位（低）
; SCLK expected low on entry. Return with SCK, SDA low.
ACKK:	CLR	SDA		;ACKK bit
	NOP			;enforce SCK low and data setup
	SETB	SCK		;raise clock
	NOP			;延时
	NOP	
	CLR	SCK		;drop clock
	RET
;---------------------------------------
;发送确认位（高）
; SCLK expected low on entry. Return with SCK low, SDA high.
NAK:	SETB	SDA		;NAK bit
	NOP			;enforce SCK low and data setup
	SETB	SCK		;raise clock
	NOP			;延时
	NOP	
	CLR	SCK		;drop clock
	RET


END