免费文档范文--大棚温室自动控制系统文档设计(九)

bsp;a, FADDR 
 SETB acc.0  
 LCALL    shout        
 JC x44
 LCALL    shin          
 LCALL    NAK           
 CLR c  
x44:LCALL    stop
x45:ret
rd_rand:NOP
 ; AT24Cxx Random Read function.
 ;Called with programmable address in A, byte address in
 ; register pair ADDR_HI:ADDR_LO. Returns data in A.
 ; Returns CY set to indicate that the bus is not available
 ; or that the addressed device failed to acknowledge.
 PUSH b
 MOV b, a
  LCALL    start
 JC x47  
 RL a  
 ORL a, FADDR 
 CLR acc.0  
 LCALL    shout     
 JC x46  
 MOV a, address 
 LCALL    shout         
 JC x46        
 MOV a, b
 LCALL rd_curr
 LJMP x47            
x46: LCALL    stop
x47: pop     b
 ret
start:NOP
 ; Send START, defined as high-to-low SDA with SCL high.
 ; Return with SCL, SDA low.
 ; Returns CY set if bus is not available.
 setb SDA
 setb SCL; Verify bus available.
 jnb SDA, x40 
 jnb SCL, x40 
 nop   
 clr SDA
 nop   
 nop   
 nop   
 nop   
 nop   
 clr SCL
 clr c  
 Ljmp     x41
 x40:    setb    c              
 x41:    ret;;
 stop: NOP
 ; Send STOP, defined as low-to-high SDA with SCL high.
 ; SCL expected low on entry. Return with SCL, SDA high.
 clr SDA
 nop   
 nop
 setb SCL
 nop  
 nop   
 nop   
 nop   
 nop   
 setb SDA
 ret
 shout:NOP
 ; Shift out a byte to the AT24Cxx, most significant bit first.
 ; SCL, SDA expected low on entry. Return with SCL low.
 ; Called with data to send in A.
 ; Returns CY set to indicate failure by slave to acknowledge.
 ; Destroys A.
 push b
 mov b, #8  
x42: NOP
 rlc a  
 mov SDA, c  
 nop   
 setb SCL  
 nop  
 nop   
 nop   
 nop   
 clr SCL

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