avr_200_b.asm

Collected AVR assembler code samples to learn assembler. I use it in my classes.

	rjmp	d8u_10		;else
d8u_9:	sec			;    set carry to be shifted into result

d8u_10:	rol	dd8u		;shift left dividend
	rol	drem8u		;shift dividend into remainder
	sub	drem8u,dv8u	;remainder = remainder - divisor
	brcc	d8u_11		;if result negative
	add	drem8u,dv8u	;    restore remainder
	clc			;    clear carry to be shifted into result
	rjmp	d8u_12		;else
d8u_11:	sec			;    set carry to be shifted into result

d8u_12:	rol	dd8u		;shift left dividend
	rol	drem8u		;shift dividend into remainder
	sub	drem8u,dv8u	;remainder = remainder - divisor
	brcc	d8u_13		;if result negative
	add	drem8u,dv8u	;    restore remainder
	clc			;    clear carry to be shifted into result
	rjmp	d8u_14		;else
d8u_13:	sec			;    set carry to be shifted into result

d8u_14:	rol	dd8u		;shift left dividend
	rol	drem8u		;shift dividend into remainder
	sub	drem8u,dv8u	;remainder = remainder - divisor
	brcc	d8u_15		;if result negative
	add	drem8u,dv8u	;    restore remainder
	clc			;    clear carry to be shifted into result
	rjmp	d8u_16		;else
d8u_15:	sec			;    set carry to be shifted into result

d8u_16:	rol	dd8u		;shift left dividend
	ret


;***************************************************************************
;*
;* "div16u" - 16/16 Bit Unsigned Division
;*
;* This subroutine divides the two 16-bit numbers 
;* "dd8uH:dd8uL" (dividend) and "dv16uH:dv16uL" (divisor). 
;* The result is placed in "dres16uH:dres16uL" and the remainder in
;* "drem16uH:drem16uL".
;*  
;* Number of words	:196 + return
;* Number of cycles	:148/173/196 (Min/Avg/Max)
;* Low registers used	:2 (drem16uL,drem16uH)
;* High registers used  :4 (dres16uL/dd16uL,dres16uH/dd16uH,dv16uL,dv16uH)
;*
;***************************************************************************

;***** Subroutine Register Variables

.def	drem16uL=r14
.def	drem16uH=r15
.def	dres16uL=r16
.def	dres16uH=r17
.def	dd16uL	=r16
.def	dd16uH	=r17
.def	dv16uL	=r18
.def	dv16uH	=r19

;***** Code

div16u:	clr	drem16uL	;clear remainder Low byte
	sub	drem16uH,drem16uH;clear remainder High byte and carry

	rol	dd16uL		;shift left dividend
	rol	dd16uH
	rol	drem16uL	;shift dividend into remainder
	rol	drem16uH
	sub	drem16uL,dv16uL	;remainder = remainder - divisor
	sbc	drem16uH,dv16uH	;
	brcc	d16u_1		;if result negative
	add	drem16uL,dv16uL	;    restore remainder
	adc	drem16uH,dv16uH
	clc			;    clear carry to be shifted into result
	rjmp	d16u_2		;else
d16u_1:	sec			;    set carry to be shifted into result

d16u_2:	rol	dd16uL		;shift left dividend
	rol	dd16uH
	rol	drem16uL	;shift dividend into remainder
	rol	drem16uH
	sub	drem16uL,dv16uL	;remainder = remainder - divisor
	sbc	drem16uH,dv16uH	;
	brcc	d16u_3		;if result negative
	add	drem16uL,dv16uL	;    restore remainder
	adc	drem16uH,dv16uH
	clc			;    clear carry to be shifted into result
	rjmp	d16u_4		;else
d16u_3:	sec			;    set carry to be shifted into result

d16u_4:	rol	dd16uL		;shift left dividend
	rol	dd16uH
	rol	drem16uL	;shift dividend into remainder
	rol	drem16uH
	sub	drem16uL,dv16uL	;remainder = remainder - divisor
	sbc	drem16uH,dv16uH	;
	brcc	d16u_5		;if result negative
	add	drem16uL,dv16uL	;    restore remainder
	adc	drem16uH,dv16uH
	clc			;    clear carry to be shifted into result
	rjmp	d16u_6		;else
d16u_5:	sec			;    set carry to be shifted into result

d16u_6:	rol	dd16uL		;shift left dividend
	rol	dd16uH
	rol	drem16uL	;shift dividend into remainder
	rol	drem16uH
	sub	drem16uL,dv16uL	;remainder = remainder - divisor
	sbc	drem16uH,dv16uH	;
	brcc	d16u_7		;if result negative
	add	drem16uL,dv16uL	;    restore remainder
	adc	drem16uH,dv16uH
	clc			;    clear carry to be shifted into result
	rjmp	d16u_8		;else
d16u_7:	sec			;    set carry to be shifted into result

d16u_8:	rol	dd16uL		;shift left dividend
	rol	dd16uH
	rol	drem16uL	;shift dividend into remainder
	rol	drem16uH
	sub	drem16uL,dv16uL	;remainder = remainder - divisor
	sbc	drem16uH,dv16uH	;
	brcc	d16u_9		;if result negative
	add	drem16uL,dv16uL	;    restore remainder
	adc	drem16uH,dv16uH
	clc			;    clear carry to be shifted into result
	rjmp	d16u_10		;else
d16u_9:	sec			;    set carry to be shifted into result

d16u_10:rol	dd16uL		;shift left dividend
	rol	dd16uH
	rol	drem16uL	;shift dividend into remainder
	rol	drem16uH
	sub	drem16uL,dv16uL	;remainder = remainder - divisor
	sbc	drem16uH,dv16uH	;
	brcc	d16u_11		;if result negative
	add	drem16uL,dv16uL	;    restore remainder
	adc	drem16uH,dv16uH
	clc			;    clear carry to be shifted into result
	rjmp	d16u_12		;else
d16u_11:sec			;    set carry to be shifted into result

d16u_12:rol	dd16uL		;shift left dividend
	rol	dd16uH
	rol	drem16uL	;shift dividend into remainder
	rol	drem16uH
	sub	drem16uL,dv16uL	;remainder = remainder - divisor
	sbc	drem16uH,dv16uH	;
	brcc	d16u_13		;if result negative
	add	drem16uL,dv16uL	;    restore remainder
	adc	drem16uH,dv16uH
	clc			;    clear carry to be shifted into result
	rjmp	d16u_14		;else
d16u_13:sec			;    set carry to be shifted into result

d16u_14:rol	dd16uL		;shift left dividend
	rol	dd16uH
	rol	drem16uL	;shift dividend into remainder
	rol	drem16uH
	sub	drem16uL,dv16uL	;remainder = remainder - divisor
	sbc	drem16uH,dv16uH	;
	brcc	d16u_15		;if result negative
	add	drem16uL,dv16uL	;    restore remainder
	adc	drem16uH,dv16uH
	clc			;    clear carry to be shifted into result
	rjmp	d16u_16		;else
d16u_15:sec			;    set carry to be shifted into result

d16u_16:rol	dd16uL		;shift left dividend
	rol	dd16uH
	rol	drem16uL	;shift dividend into remainder
	rol	drem16uH
	sub	drem16uL,dv16uL	;remainder = remainder - divisor
	sbc	drem16uH,dv16uH	;
	brcc	d16u_17		;if result negative
	add	drem16uL,dv16uL	;    restore remainder
	adc	drem16uH,dv16uH
	clc			;    clear carry to be shifted into result
	rjmp	d16u_18		;else
d16u_17:	sec			;    set carry to be shifted into result

d16u_18:rol	dd16uL		;shift left dividend
	rol	dd16uH
	rol	drem16uL	;shift dividend into remainder
	rol	drem16uH
	sub	drem16uL,dv16uL	;remainder = remainder - divisor
	sbc	drem16uH,dv16uH	;
	brcc	d16u_19		;if result negative
	add	drem16uL,dv16uL	;    restore remainder
	adc	drem16uH,dv16uH
	clc			;    clear carry to be shifted into result
	rjmp	d16u_20		;else
d16u_19:sec			;    set carry to be shifted into result

d16u_20:rol	dd16uL		;shift left dividend
	rol	dd16uH
	rol	drem16uL	;shift dividend into remainder
	rol	drem16uH
	sub	drem16uL,dv16uL	;remainder = remainder - divisor
	sbc	drem16uH,dv16uH	;
	brcc	d16u_21		;if result negative
	add	drem16uL,dv16uL	;    restore remainder
	adc	drem16uH,dv16uH
	clc			;    clear carry to be shifted into result
	rjmp	d16u_22		;else
d16u_21:sec			;    set carry to be shifted into result

d16u_22:rol	dd16uL		;shift left dividend
	rol	dd16uH
	rol	drem16uL	;shift dividend into remainder
	rol	drem16uH
	sub	drem16uL,dv16uL	;remainder = remainder - divisor
	sbc	drem16uH,dv16uH	;
	brcc	d16u_23		;if result negative
	add	drem16uL,dv16uL	;    restore remainder
	adc	drem16uH,dv16uH
	clc			;    clear carry to be shifted into result
	rjmp	d16u_24		;else
d16u_23:sec			;    set carry to be shifted into result

d16u_24:rol	dd16uL		;shift left dividend
	rol	dd16uH
	rol	drem16uL	;shift dividend into remainder
	rol	drem16uH
	sub	drem16uL,dv16uL	;remainder = remainder - divisor
	sbc	drem16uH,dv16uH	;
	brcc	d16u_25		;if result negative
	add	drem16uL,dv16uL	;    restore remainder
	adc	drem16uH,dv16uH
	clc			;    clear carry to be shifted into result
	rjmp	d16u_26		;else
d16u_25:sec			;    set carry to be shifted into result

d16u_26:rol	dd16uL		;shift left dividend
	rol	dd16uH
	rol	drem16uL	;shift dividend into remainder
	rol	drem16uH
	sub	drem16uL,dv16uL	;remainder = remainder - divisor
	sbc	drem16uH,dv16uH	;
	brcc	d16u_27		;if result negative
	add	drem16uL,dv16uL	;    restore remainder
	adc	drem16uH,dv16uH
	clc			;    clear carry to be shifted into result
	rjmp	d16u_28		;else
d16u_27:sec			;    set carry to be shifted into result

d16u_28:rol	dd16uL		;shift left dividend
	rol	dd16uH
	rol	drem16uL	;shift dividend into remainder
	rol	drem16uH
	sub	drem16uL,dv16uL	;remainder = remainder - divisor
	sbc	drem16uH,dv16uH	;
	brcc	d16u_29		;if result negative
	add	drem16uL,dv16uL	;    restore remainder
	adc	drem16uH,dv16uH
	clc			;    clear carry to be shifted into result
	rjmp	d16u_30		;else
d16u_29:sec			;    set carry to be shifted into result

d16u_30:rol	dd16uL		;shift left dividend
	rol	dd16uH
	rol	drem16uL	;shift dividend into remainder
	rol	drem16uH
	sub	drem16uL,dv16uL	;remainder = remainder - divisor
	sbc	drem16uH,dv16uH	;
	brcc	d16u_31		;if result negative
	add	drem16uL,dv16uL	;    restore remainder
	adc	drem16uH,dv16uH
	clc			;    clear carry to be shifted into result
	rjmp	d16u_32		;else
d16u_31:sec			;    set carry to be shifted into result

d16u_32:rol	dd16uL		;shift left dividend
	rol	dd16uH
	ret



;****************************************************************************
;*
;* Test Program
;*
;* This program calls all the subroutines as an example of usage and to 
;* verify correct verification.
;*
;****************************************************************************

;***** Main Program Register variables

.def	temp	=r16		;temporary storage variable

;***** Code
RESET:
;---------------------------------------------------------------
;Include these lines for devices with SRAM
;	ldi	temp,low(RAMEND)
;	out	SPL,temp	
;	ldi	temp,high(RAMEND)
;	out	SPH,temp	;init Stack Pointer
;---------------------------------------------------------------

;***** Multiply Two Unsigned 8-Bit Numbers (250 * 4)

	ldi	mc8u,250
	ldi	mp8u,4
	rcall	mpy8u		;result: m8uH:m8uL = $03e8 (1000)

;***** Multiply Two Unsigned 16-Bit Numbers (5050 * 10,000)
	ldi	mc16uL,low(5050)
	ldi	mc16uH,high(5050)
	ldi	mp16uL,low(10000)
	ldi	mp16uH,high(10000)
	rcall	mpy16u		;result: m16u3:m16u2:m16u1:m16u0
				;=$030291a0 (50,500,000)

;***** Divide Two Unsigned 8-Bit Numbers (100/3)
	ldi	dd8u,100
	ldi	dv8u,3
	rcall	div8u		;result: 	$21 (33)
				;remainder:	$01 (1)

;***** Divide Two Unsigned 16-Bit Numbers (50,000/24,995)
	ldi	dd16uL,low(50000)
	ldi	dd16uH,high(50000)
	ldi	dv16uL,low(24995)
	ldi	dv16uH,high(24995)
	rcall	div16u		;result:	$0002 (2)
				;remainder:	$000a (10)

forever:rjmp	forever