一个例子,请仔细阅读
;Assume:
CpuClck EQU 12000 ;12000Khz=12Mhz
TmrClck EQU CpuClck/12;1M=1000K
ReferF EQU 1000;HZ=1khz
ReferT EQU 1000;us=1ms
WatchedF EQU 40;KHZ=0x28
CurrTH1 EQU R0
CurrTL1 EQU R1
LastTH1 EQU R2
LastTL1 EQU R3
DeltTH1 EQU R4
DeltTL1 EQU R5
Cmppare EQU R6
ORG 0000H
LJMP STAR
;;;;;;;;;;;;;;;;;;;;;;;;
ORG 000BH
;T0 Int
PUSH PSW
PUSH ACC;save waht we used
CLR TR0
ACALL ReReadT1
;T1 in R0,R1;Delta=Current-Last
CLR C
MOV A,CurrTL1
SUBB A,LastTL1
MOV DeltTL1,A
MOV A,CurrTH1
SUBB A,LastTH1
MOV DeltTH1,A
;update
MOV A,CurrTL1
MOV LastTL1,A
MOV A,CurrTH1
MOV LastTH1,A
;
CLR C
MOV A,DeltTL1
SUBB A,#Low(WatchedF)
JC Less;<
;>=
MOV A,DeltTH1
SUBB A,#High(WatchedF)
JC Less;<
;>=
INC Cmppare;
MOV A,Cmppare
;
SUBB A,#5
JC Less;<5
;if >5 do something
; MOV P3,#0;
Less:
;Re Set T0
MOV TH0,#High(-ReferT)
MOV TL0,#Low(-ReferT)
SETB TR0
POP ACC;restore
POP PSW
RETI
;;;;;;;;;;;;;;;;;;;;;;;;;;
ReReadT1:;T1 still counts
MOV A,TH1
MOV CurrTL1,TL1
;if a carry from low byte to high byte occures,
;we read it again.
CJNE A,TH1,ReReadT1
MOV CurrTH1,A
JNB TF1,NotTF1;TF1
;TF1
CLR TF1
NotTF1:
RET
;;;;;;;;;;;;;;;;;;;;;;;;;;
;main
STAR:
MOV SP,#70h
MOV P3,0FFH
MOV TMOD,#0101$0001B;T1=16 ¼ÇÊý,T0=16 ¶¨Ê±
;
MOV TH0,#High(-ReferT)
MOV TL0,#Low(-ReferT)
;
MOV TH1,#0
MOV TL1,#0
MOV Cmppare,0
;
SETB EA
;
SETB ET0
SETB TR0
SETB TR1
LOOP:
#define SIMULATE
;comment above if run on target
#ifdef SIMULATE
;T1+1
INC TL1
MOV A,TL1
JNZ goon
;high byte +1
INC TH1
goon:;add NOP to adjust the watched frequency
NOP
NOP
NOP
NOP
NOP
NOP
NOP
NOP
NOP
NOP
;10us
NOP
NOP
NOP
NOP
NOP
NOP
NOP
NOP
NOP;40KHZ
#endif
JMP LOOP
END
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