;->R22: new data in the upper nibble
	lsr R22			; 1
	andi R22,$78	; 1
	eor R23,R22		; 1
	mov R22,R23		; 1 
	swap R23		; 1
	andi R23,$88	; 1
	mov R21,R22		; 1
	lsr R21			; 1
	andi R21,$38	; 1
	eor R23,R21		; 1
	lsl R22			; 1
	eor R23,R22		; 1
	lsl R22			; 1
	andi R22,$20	; 1
	eor R23,R22		; 1
					;--
					;15
												
;it's the code for one nibble, there is a code variant for
;three bits only:

;->R22: new data in the lower three bits of upper nibble
	lsr R22			; 1
	andi R22,$38	; 1
	eor R23,R22		; 1
	mov R22,R23		; 1
	mov R21,R23		; 1
	andi R23,$38	; 1
	swap R21		; 1
	lsl R21			; 1
	andi R21,3		; 1
	eor R23,R21		; 1
	lsl R22			; 1	
	lsl R22			; 1
	eor R23,R22		; 1
					;--
					;13