Ответ: («Телесистемы»: Конференция «Микроконтроллеры и их применение»)

;
;code taken from: http://www.roboternetz.de/phpBB2/viewtopic.php?p=241756&sid=b09545346b1e65e9c2a80eab406dc46c#241756
; coder: BellaD ,  http://www.roboternetz.de/phpBB2/profile.php?mode=viewprofile&u=24278
;
.include "2313def.inc"

; **** Random number generator ************************************

.def	RAND1		=R7	;Random number generator needs three
.def	RAND2		=R8	;bytes. This could just as well be
.def	RAND3		=R9	;SRAM, but it would be a little slower
.def	TEMP		=R16




rjmp RESET 	; Reset Handler




Reset:
		
		ldi r16,low(RAMEND); Main program start
		out SPL,r16			; !!!!! Set Stack pointer 2313 only low byte ,hasn't 16 bit
		rcall Init_Random


;******************************************************************

main:
		rcall Random
		nop
		rjmp main
		

;******************************************************************
Init_Random:
	ldi	TEMP,$AA	;Init the random number generator 
	mov	RAND1,TEMP	;since a 00,00,00 state will not 
	mov	RAND2,TEMP	;progress.
	mov	RAND3,TEMP	;
	ret


;********************** Random Number *****************************
;* for random action maybe , not used yet ! works fine
;******************************************************************
Random:
	;Maximal legnth 19 bit shift register sequence,
	push	R16		;Make workspace
	push	R17		;

	;  RAND3    RAND2    RAND1
	;22222111 11111110 00000000
	;43210987 65432109 87654321

	mov	R16,RAND1	;Make copy
	mov	R17,RAND3	;Make copy

	;clc			;not needed, because we will overwrite bit 0 later
	rol	RAND1		;Shift the bits D7->Carry
	rol	RAND2		;Carry->D0 D7->Carry
	rol	RAND3		;Carry->D0 D7->Carry, but that will be fixed.

	;Now we have to Xor the bits to see what
	;goes in to bit 1

	rol	R17		;Move bit 19->20
	andi	R17,$08		;Important that D1,0 be zero

	andi	R16,$13		;Mask out irrelevants, protecting bit 19
	or	R17,R16		;Get bits 5->21 2->18 1->17

	andi	R17,$18		;Nuke bits 18,17
	lsr	R17		;19->19 5->20
	lsr	R17		;19->18 5->19
	lsr	R17		;19->17 5->18

	eor	R17,R16		;First xor, result in R17 (5x2 in 02 and 19x1 in 01)
	mov	R16,R17		;Make a copy
	ror	R16		;Move the 5x2 result to 01
	andi	R17,$01		;Mask off everything else
	andi	R16,$01		;in both
	eor	R17,R16		;
	brne	D_One		;If one, do that, else 

D_Zero:	
	;Set a zero in the lsb of the low byte
	mov	R16,RAND1	;Get the low byte
	andi	R16,$FE		;Make the LSB zero
	mov	RAND1,R16	;Put it back
	Rjmp	D_Exit		;Bye bye

D_One:	
	;Set a one in the lsb of the low byte
	mov	R16,RAND1	;Get the low byte
	ori	R16,$01		;Make the LSB one
	mov	RAND1,R16	;Put it back

D_Exit:
	pop	R17		;Put everything back where I got it.
	pop	R16		;
	ret
;*************************************************************************
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