.TITLE	MG07.. GENERAL PROCEDURES IN MACRO
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	.IDENT	/MG07../
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	.PAGE
	.SBTTL GENERAL PURPOSE REGISTER UTILITY SUBROUTINES R$ GROUP
	.SBTTL	.	BIT POSITION INDICATION ROUTINE
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R$BITPOS::
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;		ENTRY CONDITIONS
;	R1 =  BIT MASK
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;		EXIT CONDITIONS
;	R1 =  POSITION OF LOWEST BIT IN MASK IF STATUS = SUCCESS
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	MOV R0,-(SP)		;SAVE WORK REGISTER
	TST R1			;ARE ANY BITS SET
	BEQ	20$		;J IF NO BITS SET
	CLR R0			;ASSUME BOTTOM BIT SET
10$:	BIT #1,R1		;IS BOTTOM BIT SET
	BNE	30$		;J IF BIT SET
	INC R0			;LOOK TO NEXT BIT POSITION
	ASR R1			;SHIFT ALL BITS ONE PLACE RIGHT
	BR	10$		;TRY NEXT POSITION
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20$:	SETERROR 40$		;SET ERROR FLAG AND THEN TO RETURN SECTION
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30$:	SETSUCCESS		;INDICATE BIT FOUND
40$:	MOV R0,R1		;HOLD POSITION OF BIT
	MOV (SP)+,R0		;RESTORE REGISTER R0
	RETURN			;BACK TO CALLING PROGRAM
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	.END
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