*	XORSHIFT PRNG DEMO PROGRAM
*	FOR THE UNEXPANDED TI-99/4A
*	MICHAEL MARTIN, 2024

	IDT	'XORSHIFT'

*	CARTRIDGE HEADER
	AORG	>6000

	DATA	>AA01,0,0,MENU
	DATA	0,0,0,0
MENU	DATA	0,MAIN
	BYTE	13
	TEXT	'XORSHIFT DEMO'

*	MAIN PROGRAM

	COPY	'vdplib.asm'

MAIN	LWPI	>8300		* SET WORKSPACE
	LIMI	0		* DISABLE INTERRUPTS
	LI	R9,1		* SEED RNG
	LI	R10,1
	.VFILL	>0000,>20,>0300	* CLEAR SCREEN
	BL	@STDCHR		* SET STANDARD CHARSET
	.VFILL	>0968,>00,>08	* CLEAR DASH CHARACTER
	.VWRITE	>0969,>FF	* AND REPLACE WITH UNDERLINE
	LI	R8,>40C2	* LEAVE ROOM FOR HEADER
	LI	R4,64		* 64 ITERATIONS
LP	BL	@RNG
	BL	@PHEX
	DEC	R4
	JNE	LP
	.VBLIT	>0044,HDR,HDRLEN
	.VBLIT	>0000,FRAME,FRAMELEN
	LI	R8,>4000 | FRAMELEN
INF	MOV	R8,R7
	MOV	@>8378,R0
	ANDI	R0,255
	BL	@PHEX
	MOV	R7,R8
	JMP	INF		* LOOP FOREVER ONCE DONE

RNG	MOV	R9,R0
	SLA	R0,5
	XOR	R9,R0
	MOV	R0,R9
	SRL	R0,3
	XOR	R9,R0
	XOR	R10,R0
	MOV	R10,R9
	SRL	R10,1
	XOR	R0,R10
	MOV	R10,R0
	B	*R11

PHEX	LIMI	0
	MOV	R0,R1
	MOV	R11,R2
	SWPB	R8
	MOVB	R8,@>8C02
	SWPB	R8
	MOVB	R8,@>8C02
	SRL	R0,4
	BL	@PDIGI
	MOV	R1,R0
	BL	@PDIGI
	SWPB	R1
	MOV	R1,R0
	SRL	R0,4
	BL	@PDIGI
	MOV	R1,R0
	BL	@PDIGI
	MOV	R1,R0
	LI	R1,>2000
	MOV	R1,@>8C00
	AI	R8,8
	MOV	R1,@>8C00
	NOP
	MOV	R1,@>8C00
	NOP
	MOV	R1,@>8C00
	LIMI	2
	B	*R2
PDIGI	ANDI	R0,>0F00
	AI	R0,>3000
	CI	R0,>3A00
	JL	POK
	AI	R0,>0700
POK	MOVB	R0,@>8C00
	B	*R11

HDR	TEXT	'XORSHIFT16 TEST SEQUENCE        '
	TEXT	'------------------------'
HDRLEN	EQU	$-HDR

FRAME	TEXT	'FRAME COUNT: '
FRAMELEN	EQU	$-FRAME
	EVEN

	END MAIN