byte2asc.asm

来自「8051 进行加解密的源代码」· 汇编 代码 · 共 59 行

===============================================================================

;*******************************************************************************
;           Returns the ASCII codes from the nibbles of a byte stored in the Acc.
;           After being called the high nibble is in the Acc and the low nibble 
;           is in the B register.
;
;
;          ;usage:
;
;          mov a, #byte
;          CALL nibble
;
;          ;returns
;          ;A= high nibble
;          ;B= low nibble
;*******************************************************************************

nibble:
            mov   b,a          ; b=a        ; stores Acc in B
            anl   a,#0f0h      ; a=xxxx0000    ; A && #f0h (get the high nibble)
            swap  a            ; a=0000xxxx    ; swap nibbles
            orl   a,#30h       ; a=0011xxxx    ; add #30h, if nibble is
            push acc           ; 0-9 we have the ASCII value
            push b             ; stores A and B
            mov b, #3ah        ; stores #3ah in B
            div ab             ; divide A/#3ah
            jz, recupera1      ; if zero, nibble < #0Ah
nibble1_ok:
            pop b              ; recover B
            pop acc            ; recover A
            add a, #07h        ; adds #07h to get ASCII of A-F
            xch a,b
            jmp nibble2
recupera1:
            pop b            ; stores B
            pop acc            ; stores A
            xch a,b
nibble2:
            anl   a,#0fh        ; a=0000xxxx    ; A && #0fh (get low nibble)
            orl   a,#30h        ; a=0011xxxx    ; add #30h, if nibble is
            push acc            ; 0-9 we have the ASCII value
            push b            ; stores A and B
            mov b, #3ah            ; stores #3ah in B
            div ab            ; divide A/#3ah
            jz, recupera2        ; if zero, nibble < #0Ah
            pop b            ; recover B
            pop acc            ; recover A
            add a, #07h        ; adds #07h to get ASCII of A-F
            xch a,b
            ret                ; return to main routine
recupera2:
            pop b            ; recover B
            pop acc            ; recover A
            xch a,b
            ret                ; return to main routine

;*******************************************************************************