8086 Program to mask upper nibble

11:32


ØØ       Explanation :
·            Let the 8 bit number be in the AL register. We have to mask the upper nibble ie we have to separate the upper nibble. In the result only LSB number should be present.
 eg. :        AL = 67H.
0110
0111

Logically AND with 0FH
0000
1111


0000
0111
= 07H
                                  Result = 07 H, 6 is masked.
                                  Display the result.
ØØ       Algorithm :
Step I       :    Load the number in AL.
Step II     :    Mask the upper nibble.
Step III   :    Display result.
Step IV    :    Stop.
ØØ       Flowchart : Refer flowchart 4.


ØØ       Program :
.model small                                     
.data
a dw 0012H
.code
       mov     ax, @data               ; Initialize data section
       mov     ds, ax
       mov     ax, a                      ; Load number1 in ax
       and      al, 0fh                    ; mask upper nibble.Result in al
       mov     ch, 02h                  ; Count of digits to be displayed
       mov     cl, 04h          ; Count to roll by 4 bits
       mov     bh, al                     ; Result in reg bh
l2:    rol       bh, cl                     ; roll bl so that msb comes to lsb
       mov     dl, bh                    ; load dl with data to be displayed
       and      dl, 0fH          ; get only lsb
       cmp     dl, 09                    ; check if digit is 0-9 or letter A-F
       jbe       l4
       add      dl, 07                    ; if letter add 37H else only add 30H
l4:    add      dl, 30H
       mov     ah, 02                    ; Function 2 under INT 21H (Display character)
       int       21H
       dec      ch                         ; Decrement Count
       jnz       l2
       mov     ah, 4ch
       int       21h
       end
ØØ       Result :
C:\programs>tasm upnib.asm
Turbo Assembler  Version 3.0  Copyright (c) 1988, 1991 Borland International
Assembling file:   upnib.asm
Passes:            1
Remaining memory:  438k
C:\programs>tlink upnib
Turbo Link  Version 3.0 Copyright (c) 1987, 1990 Borland International
Warning: No stack
C:\programs>upnib
02
C:\programs>