47 lines
1.5 KiB
NASM
47 lines
1.5 KiB
NASM
; receiving the data in 'dx'
|
|
; For the examples we'll assume that we're called with dx=0x1234
|
|
print_hex:
|
|
pusha
|
|
|
|
mov cx, 0 ; our index variable
|
|
|
|
; Strategy: get the last char of 'dx', then convert to ASCII
|
|
; Numeric ASCII values: '0' (ASCII 0x30) to '9' (0x39), so just add 0x30 to byte N.
|
|
; For alphabetic characters A-F: 'A' (ASCII 0x41) to 'F' (0x46) we'll add 0x40
|
|
; Then, move the ASCII byte to the correct position on the resulting string
|
|
hex_loop:
|
|
cmp cx, 4 ; loop 4 times
|
|
je end
|
|
|
|
; 1. convert last char of 'dx' to ascii
|
|
mov ax, dx ; we will use 'ax' as our working register
|
|
and ax, 0x000f ; 0x1234 -> 0x0004 by masking first three to zeros
|
|
add al, 0x30 ; add 0x30 to N to convert it to ASCII "N"
|
|
cmp al, 0x39 ; if > 9, add extra 8 to represent 'A' to 'F'
|
|
jle step2
|
|
add al, 7 ; 'A' is ASCII 65 instead of 58, so 65-58=7
|
|
|
|
step2:
|
|
; 2. get the correct position of the string to place our ASCII char
|
|
; bx <- base address + string length - index of char
|
|
mov bx, HEX_OUT + 5 ; base + length
|
|
sub bx, cx ; our index variable
|
|
mov [bx], al ; copy the ASCII char on 'al' to the position pointed by 'bx'
|
|
ror dx, 4 ; 0x1234 -> 0x4123 -> 0x3412 -> 0x2341 -> 0x1234
|
|
|
|
; increment index and loop
|
|
add cx, 1
|
|
jmp hex_loop
|
|
|
|
end:
|
|
; prepare the parameter and call the function
|
|
; remember that print receives parameters in 'bx'
|
|
mov bx, HEX_OUT
|
|
call print
|
|
|
|
popa
|
|
ret
|
|
|
|
HEX_OUT:
|
|
db '0x0000',0 ; reserve memory for our new string
|