Need some help with keyboard BIOS Services interrupts->

[Peter Swinkels]

Whenever I use INT 16h, 1h (Keyboard BIOS Services - Get Keystroke Status) I only get the status for the first key pressed. When calling the function again I still get the status for the first key pressed while having pressed other keys. Here is the code I am using:

(I think only the part up to the ".ScanCode db "0000", 13, 10, "$"" line is important here)

ORG 256
Main:
	; Get scan code and ASCII character of any key currently being pressed.
	MOV ah, 1		; Get keyboard status.
	INT 22			; Keyboard BIOS services.

	; Convert scan code and ASCII character to user readable format.
	PUSH ax
	CALL cv256to16
	POP DWORD [.ScanCode]

	; Displays key scan code and ASCII character.
	MOV ah, 9		; Print string.
	MOV dx, .ScanCode	;
	INT 33			; DOS functions interrupt.
JMP Main

.ScanCode db "0000", 13, 10, "$"


;+-------------------------------------------------------------------------------+
;| Convert Byte to Hexadecimal - Converts byte values to hexadecimal number.     |
;| [Parameters in:]                                                 		 |
;| Name:	Description:				Type:    		 |
;| Number	Byte values to be converted.            2 Byte number (by value) |
;| Parameters out:]                                                     	 |
;| Name:	Description:				Type:    		 |
;| Hexadecimal	Converted hexadecimal number.		4 Byte string (by value) |
;+-------------------------------------------------------------------------------+

cv256to16:
	POP WORD [.ReturnAddress]
	POP WORD [.ByteVal]

	MOV bx, 0					; Digit = 0
	MOV cl, 12					; BitShift = 12
	MOV dx, 64410					; BitMask = 64410
		.GetHexDigits:
			MOV ax, [.ByteVal]		;
			AND ax, dx			; Extract a 4 bit value from the byte values.
			SHR ax, cl			;
			MOV si, ax			;
			MOV al, [.HexDigits + si]	; Get the hexadecimal digit for the 4 bit value.
			MOV [.HexNumber + bx], al	;
			SHR dx, 4			; Adjust BitMask
			SUB cl, 4			; and BitShift.
			INC bx				; Next digit.
			CMP bx, 4			; Check for last digit.
		JNE .GetHexDigits

	PUSH DWORD [.HexNumber]
	PUSH WORD [.ReturnAddress]
RET

.ByteVal dw 0
.HexNumber db "0000"
.HexDigits db "0123456789ABCDEF"
.ReturnAddress dw 0

Do I need to reset something after having called int 16h, 1h before calling the interrupt again?

Notes:
1 I have tried using Extended Get Keystroke Status (INT 16h, 11h) supposedly the ZF flag will indicate whether the key is being or was being pressed.
2 In my code all numbers are written in decimal format which means that in the code int 16h is referred to as int 22.
3 I looked up all the information about int 22h, 1h using Helppc.

[Maven]

Whenever I use INT 16h, 1h (Keyboard BIOS Services - Get Keystroke Status) I only get the status for the first key pressed. When calling the function again I still get the status for the first key pressed while having pressed other keys. Here is the code I am using:

(I think only the part up to the ".ScanCode db "0000", 13, 10, "$"" line is important here)

ORG 256
Main:
	; Get scan code and ASCII character of any key currently being pressed.
	MOV ah, 1		; Get keyboard status.
	INT 22			; Keyboard BIOS services.

	; Convert scan code and ASCII character to user readable format.
	PUSH ax
	CALL cv256to16
	POP DWORD [.ScanCode]

	; Displays key scan code and ASCII character.
	MOV ah, 9		; Print string.
	MOV dx, .ScanCode	;
	INT 33			; DOS functions interrupt.
JMP Main

.ScanCode db "0000", 13, 10, "$"


;+-------------------------------------------------------------------------------+
;| Convert Byte to Hexadecimal - Converts byte values to hexadecimal number.     |
;| [Parameters in:]                                                 		 |
;| Name:	Description:				Type:    		 |
;| Number	Byte values to be converted.            2 Byte number (by value) |
;| Parameters out:]                                                     	 |
;| Name:	Description:				Type:    		 |
;| Hexadecimal	Converted hexadecimal number.		4 Byte string (by value) |
;+-------------------------------------------------------------------------------+

cv256to16:
	POP WORD [.ReturnAddress]
	POP WORD [.ByteVal]

	MOV bx, 0					; Digit = 0
	MOV cl, 12					; BitShift = 12
	MOV dx, 64410					; BitMask = 64410
		.GetHexDigits:
			MOV ax, [.ByteVal]		;
			AND ax, dx			; Extract a 4 bit value from the byte values.
			SHR ax, cl			;
			MOV si, ax			;
			MOV al, [.HexDigits + si]	; Get the hexadecimal digit for the 4 bit value.
			MOV [.HexNumber + bx], al	;
			SHR dx, 4			; Adjust BitMask
			SUB cl, 4			; and BitShift.
			INC bx				; Next digit.
			CMP bx, 4			; Check for last digit.
		JNE .GetHexDigits

	PUSH DWORD [.HexNumber]
	PUSH WORD [.ReturnAddress]
RET

.ByteVal dw 0
.HexNumber db "0000"
.HexDigits db "0123456789ABCDEF"
.ReturnAddress dw 0

Do I need to reset something after having called int 16h, 1h before calling the interrupt again?

Notes:
1 I have tried using Extended Get Keystroke Status (INT 16h, 11h) supposedly the ZF flag will indicate whether the key is being or was being pressed.
2 In my code all numbers are written in decimal format which means that in the code int 16h is referred to as int 22.
3 I looked up all the information about int 22h, 1h using Helppc.

I don't have a 16 bit assembler anywhere so I can't test this... but if memory serves me well, the function you want to call is 10h not 1h.

IE: mov ah, 10h
int 16h
peace.

[Peter Swinkels]

Function 10h makes the program wait for the user to press a key. I want to check if a key is being pressed.

[Maven]

doh my bad =P

on a 122 keyboard, it's al = 21h

on a enhanced keyboard its 11h

on some systems the 1st one is an alais for the 2nd one. Also just know that they don't remove things from the buffer, the scan code is in ah and the ascii code is in al.

[Maven]

doh my bad =P

on a 122 keyboard, it's al = 21h

on a enhanced keyboard its 11h

on some systems the 1st one is an alais for the 2nd one. Also just know that they don't remove things from the buffer, the scan code is in ah and the ascii code is in al.

int 16h btw