9086/boot_code/helpers.asm

;Input AX
PRINT_16_HEX:
PUSH DX

TEST AH,#0xF0
jz NOT_FIRST_NIBBLE
MOV DL,AH
CALL PRINT_HIGH
JMP SKIP1

NOT_FIRST_NIBBLE:
TEST AH,#0x0F
jz NOT_SECOND_NIBBLE
SKIP1:
MOV DL,AH
CALL PRINT_LOW
JMP SKIP2

NOT_SECOND_NIBBLE:
TEST AL,#0xF0
jz NOT_THIRD_NIBBLE
SKIP2:
MOV DL,AL
CALL PRINT_HIGH

NOT_THIRD_NIBBLE:
MOV DL,AL
CALL PRINT_LOW

PUSH AX
MOV AH,#0x02
MOV DL,#0x20
INT #0x21
POP AX

POP DX
RET

PRINT_HIGH:
AND DL,#0xF0
TEST DL,#0x80
jz NOT1
OR DL,#0x08
NOT1:
TEST DL,#0x40
jz NOT2
OR DL,#0x04
NOT2:
TEST DL,#0x20
jz NOT3
OR DL,#0x02
NOT3:
TEST DL,#0x10
jz DONE
OR DL,#0x01
DONE:

PRINT_LOW:
PUSH AX
AND DL,#0x0F
CMP DL,#0x0A
JNS LETTERS
ADD DL,#0x30
MOV AH,#0x02
INT #0x21
POP AX
RET

LETTERS:
ADD DL,#0x37
MOV AH,#0x02
INT #0x21
POP AX
RET

PRINT_0_8_HEX:
MOV DL,AL

PUSH AX
CALL PRINT_HIGH
POP AX

MOV DL,AL
CALL PRINT_LOW

PUSH AX
MOV AH,#0x02
MOV DL,#0x20
INT #0x21
POP AX

RET