dectobin.asm

8051 进行加解密的源代码

;***************************************************************************;
;*      CONVERTS 5 DIGIT DECIMAL NUMBER INTO 3 BYTES BINARY NUMBER         *;
;***************************************************************************;


BIN_1           EQU     42H     ; LSB
BIN_2           EQU     41H     ; MIDDLE SB
BIN_3           EQU     40H     ; MSB

DEC_1           EQU     50H     ; TEN THOUSANDS OF 5 DIGIT DECIMAL NUMBER
DEC_2           EQU     51H     ; THOUSANDS OF 5 DIGIT DECIMAL NUMBER
DEC_3           EQU     52H     ; HUNDREDS OF 5 DIGIT DECIMAL NUMBER
DEC_4           EQU     53H     ; TENS OF 5 DIGIT DECIMAL NUMBER
DEC_5           EQU     54H     ; UNITS OF 5 DIGIT DECIMAL NUMBER

FACTOR          EQU     60H     ; AUXILLIARY VARIABLE


;***************************************************************************;
;****                           MAIN CODE                               ****:
;***************************************************************************;

;***************************************************************************;
;***                            EXAMPLE                                 ****;
;***************************************************************************;
;** TO CONVERT 5 DIGIT DECIMAL NUMBER <12345> INTO 3 BYTES BINARY NUMBER ***;
;****************************************************************************

        MOV     R2,#00	; NEW LINE
                           ;    \
        MOV     BIN_1,#00  ;    |
        MOV     BIN_2,#00  ;    |  3 BYTES BINARY OUTPUT
        MOV     BIN_3,#00  ;    |
                           ;    /


        MOV     DEC_1,#05D         ; UNITS
        MOV     DEC_2,#04D         ; TENS
        MOV     DEC_3,#03D         ; HUNDREDS
        MOV     DEC_4,#02D         ; THOUSANDS (1st Decimal place)
        MOV     DEC_5,#01D         ; TEN THOUSANDS (2nd Decimal place)

        MOV     A,DEC_1         ; TAKE THE UNITS DIRECTLY AS IT IS TO THE LSB
        MOV     BIN_1,A

        MOV     A,DEC_2         ; TAKE THE TENS BY MULTIPLYING WITH #10D AND
        MOV     B,#10           ; AND ADDING TO THE LSB
        MUL     AB
        ADD     A,BIN_1
        MOV     BIN_1,A

        MOV     R0,#52H         ; THE ADDRESS OF 3rd DIGIT 
        MOV     FACTOR,#00D     ; INITIALIZE AS ZERO
        MOV     A,@R0           ; TAKE THE 3rd DIGIT INTO R1 FOR PROCESSING
        MOV     R1,A

        CJNE    R1,#00,LOOP     ; SKIP IF THE DIGIT IS A ZERO
        SJMP    ITS_ZERO

LOOP
        MOV     A,#100D         ; ADD CONSTANT 100D TO LSB AS MANY TIMES
        CLR     C
        ADD     A,BIN_1
        MOV     BIN_1,A
        JNC     NO_EXCEED

        INC     BIN_2           ; INCREASE THE NEXT HIGHER BYTES WHEN THE LSB
        MOV     A,BIN_2         ; OVERFLOWS

        CJNE    A,#00H,NO_EXCEED
        INC     BIN_3

NO_EXCEED
        DJNZ    R1,LOOP

;-----------
        CJNE    R2,#00,CONTINUE
        SJMP    ITS_ZERO
CONTINUE
        DEC     R2
        SJMP    LOOP
;-----------

ITS_ZERO
        INC     R0              ; GET NEXT DIGIT WHEN THE LOOP EXHAUSTS
        CJNE    R0,#55H,PROCEED ; GET OUT WHEN ALL THE 3 DIGITS HAVE BEEN
                                ; WORKED UPON. (1st and 2nd digits are used
                                ;               before the loop)
        SJMP    OUT_LOOP

PROCEED
        INC     FACTOR          ; CALCULATE AS HOW MANY TIMES THE CONSTANT
        MOV     A,@R0           ; 100D HAS TO BE ADDED TO LSB DEPENDING ON
        CJNE    A,#00,NOT_ZERO  ; THE VALUE OF THE DIGIT ACQUIRED BY @R0
        SJMP    ITS_ZERO

NOT_ZERO
        PUSH    FACTOR

MULTIPLY
        MOV     B,#10D
        CLR     OV
        MUL     AB
        JNB     OV,SINGLE
        PUSH    ACC
        MOV     A,B
        ADD     A,R2
        MOV     R2,A
        POP     ACC
SINGLE
        DJNZ    FACTOR,MULTIPLY
        MOV     R1,A
        POP     FACTOR
        SJMP    LOOP

OUT_LOOP

        MOV     R1,BIN_2
        MOV     R2,BIN_1
        MOV     R0,BIN_3

        END

*****************************************************************************
IDEA:
*****************************************************************************

  LSB
+ (DEC_1)
+ (DEC_2 x 10D)
+ (DEC_3 x 1 x 100D)
+ (DEC_4 x 10 x 100D)
+ (DEC_5 x 100 x 100D)