bintoasc.asm

8051 进行加解密的源代码

;
;  +-------------------------------------------------------------------------+
;  | Purpose: Routine to convert a 16bit binary number in ASCII
;  |                                                                         |
;  | INPUT : R2 (Lsb) and R3 (Msb)   ( binary)                               |
;  |                                                                         |
;  | OUPUT : 30h,31h,32h,33h,34h  (internal RAM address)  (ASCII)            |
;  |   msb--^                  ^------lsb                                       |
;  |                                                                         |
;  | Destroy all registers                                                   |
;  |                                                                         |
;  | PROGRAMMER: Bruno Marcio Diogo Venancio ( [e-mail] )     |
;  | BRAZIL 07/19/2002                                                       |
;  |          THIS CODE CAN BE FREELY DISTRIBUTED WITHOUT CHANGES            |
;  +-------------------------------------------------------------------------+
;
; Use example:    
;                      
;START:
;        MOV R2,#low(1234)                                
;        MOV R3,#high(1234)
;        LCALL  BINTOASC
;       
;   in 30h until 34h of internal RAM will be :'0','1',' 2',','3','4' ( ASCII)
;
;
;             The Routine Algorithm
;
;
;                  +-------+
;                  | START |
;                  +---+---+
;                      |         
;                  +-------+
;                  |   N   |        ( N= Number to be coverted)
;                  +-------+
;                      |
;                +-------------+
;                | POUT   <- 0 |    ( POUT = Output address )        
;                +-------------+
;                      |
;                 +--------+
;                 | P <- 0 |      ( P= Table Index )
;                 +--------+
;                      |
;                      |
;     +----------->    | 
;     |           +-------------+ ( R = Register )
;     |           | R <- TAB(P) | ( Fetch a table number indexed by P ) 
;     |           +-------------+
;     |                |
;     |           +----------+
;     |           | C <- '0' |    ( C= counter)
;     |           +----------+    ( counter <- 0 in ASCII)
;     |                |
;     |    +------>    |
;     |    |      +-----------+
;     |    |      | N <-  N-R |   ( subtract the table number with R )
;     |    |      +-----------+                                          
;     |    |           |
;     |    |      N   /  \   Y
;     |    |     +--< N<0? >-----------+
;     |    |     |   \    /            |
;     |    |     |     \/              |
;     |    |     |             +--------------------+
;     |    |  +-------+        | TABOUT (POUT) <- C |
;     |    |  |C<- C+1|        +--------------------+
;     |    |  +-------+                |
;     |    |     |                +----------+
;     |    +-----+                | N <- N+R |
;     |                           +----------+
;     |                                |
;     |                       +------------------+
;     |                       | POUT  <- POUT +1 |
;     |                       +------------------+
;     |                                |
;     |                               /^\
;     |                             /     \
;     |   +----------+         N  /         \ S
;     +---| P <- P+1 |-----------< TAB(P)=1? > ---------+
;         +----------+            \         /           |
;                                   \     /             |
;                                     \ /               |
;                                                    +-----+
;                                                    | END |
;                                                    +-----+
;
;           
 
BINTOASC:

        MOV R0,#30h                 ; R0 = POUT 
        MOV DPTR,#TAB               ; R=TAB(P)

COM1:

        CLR A                       ; P <- 0     
        MOVC A,@A+DPTR              ; R <-  TAB(P)
        MOV R7,A
        INC DPTR
        CLR A
        MOVC A,@A+DPTR
        MOV R6,A

        MOV R4,#'0'                  ; C  <- '0'


SOMA:                                ; N <-  N-R 
      CLR C        ;              
      MOV A,R2     ;              
      SUBB A,R6    ;              
      MOV R2,A     ;              
                                 
      MOV A,R3     ;               
      SUBB A,R7    ;              
      MOV R3,A     ;              
      JC SAIDA     ;    If < 0 goto  SAIDA
      INC R4       ;    If >0 then C <- C +1
      SJMP SOMA    ;    goto SOMA            
SAIDA:
      MOV A,R4                 
      MOV @R0,A              ;TABOUT (POUT) <- C

      MOV A,R2             
      ADD A,R6               ;  N=N+R
      MOV R2,A             
                           
      MOV A,R3             
      ADDC A,R7            
      MOV R3,A             

      INC R0                 ; PSAIDA=PSAIDA +1

      CLR A
      MOVC A,@A+DPTR
      CJNE A,#1,INCREMENTA   ; TAB(P) = 1 ?
      RET                    ; If yes, END

INCREMENTA:                  ; If No, P <- P+1
      INC DPTR
      LJMP COM1              ; goto COM1


TAB:
     DW 10000
     DW 1000
     DW 100
     DW 10
     DW 1


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