8086 Program to mask lower nibble

11:30


Explanation :
·           Let the 8 bit number be in the AL register. We have to mask the lower nibble, ie we have to separate the lower nibble. In the result only MSB number should remain.
For example :




 eg. :        AL = 5B H.
0101
1011

Logically AND with F0 H
1111
0000


0101
0000
= 50 H.
                                  Result = 50 H. B is masked
                                  Display the result.
ØØ       Algorithm :
Step I            :   Load the number in AL.
Step II          :   Mask tower  nibble i.e. AND AL, 0F0 H.
Step III        :   Display result.
Step IV         :   Stop.
ØØ       Flowchart : Refer flowchart 3.

ØØ       Program :
.model smallFlowchart 3
.data
a dw 0012H
.code
       mov     ax, @data               ; Initialize data section
       mov     ds, ax
       mov     ax, a                      ; Load number1 in ax
       and      al, 0f0h                  ; mask lower 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 lownib.asm
Turbo Assembler  Version 3.0  Copyright (c) 1988,  1991 Borland International
Assembling file:   lownib.asm
Error messages:    None
Warning messages:  None
Passes:            1
Remaining memory:  438k
C:\programs>tlink lownib.obj
Turbo Link  Version 3.0 Copyright (c) 1987, 1990 Borland International
Warning: No stack
C:\programs>lownib
10
C:\programs>