* (PL$MV) REV 1.0 INCREMENTAL PLOTTER ROUTINES
*
*    
* PROGRAM TITLE:  
*                 PL$MV (PL$MV,PL$RST) 
*                 
*                 PLOTTER MOVEMENT ROUTINES
*                         
*               
* REVISIONS: 
*            1.0 (2007-05-28)
*
* AUTHOR:	
*
*    PHILIPP HACHTMANN
*
*
* PURPOSE:	
*
*    PROVIDE SIMPLE LIBRARY FUNCTIONS FOR INCREMENTAL PLOTTERS
*
*
* STORAGE:	
*
*    ??? (OCTAL)
*    ??? (DECIMAL)
*
*
* USAGE     
* 
*              CALL     PL$RST	- SET VIRTUAL PLOT POSITION TO ZERO
*
*              CALL     PL$MV   - MOVE TO POINT SPECIFIED
*              DAC	XN        BY XN
*	       DAC      YN        AND YN VALUE
*              
*
*
********************************************************************************
*
*
	SUBR	PL$MV,MOVE
	SUBR	PL$RST,RST
*
*
	REL		THIS IS A RELOCATABLE OBJECT
	ORG	'0
*
*
RST	DAC	**	SET POINT ZERO
	STA	X
	CRA
	STA	Y
	IMA	X
	JMP*	RST
*
*
MOVE	DAC	**	MOVE YA!
*	
	LDA*	MOVE	GET PARAMETERS 
	STA	TMP
	LDA*	TMP
	STA	XN
	SUB	X
	STA	DX
	IRS	MOVE
	LDA*	MOVE
	STA	TMP
	LDA*	TMP
	STA	YN
	SUB	Y
	STA	DY
	IRS	MOVE
	IRS	MOVE	CORRECT RETURN ADDRESS
*
*	HLT
*	LDA	YN
*	IAB
*	LDA	XN
*	HLT
*	JMP	1
*	
	LDA	DX
	SMI
	JMP	DXP	DX POSITIVE
*			DX NEGATIVE
	TCA		
	STA	DX	NOW, DX IS POSITIVE!
	LDA	ML
	STA	STPX
	LDA	MUL
	STA	DIYP
	LDA	MDL
	STA	DIYN
	JMP	DXNP
DXP	LDA	MR
	STA	STPX
	LDA	MUR
	STA	DIYP
	LDA	MDR
	STA	DIYN
	JMP	DXNP	
*
DXNP	LDA	DY
	SMI
	JMP	DYP	DY POSITIVE
*			DY NEGATIVE
	TCA
	STA	DY	NOW, DY IS POSITIVE!
	LDA	MD
	STA	STPY
	LDA	DIYN
	STA	STPD
	JMP	DYNP
DYP	LDA	MU
	STA	STPY
	LDA	DIYP
	STA	STPD
*
DYNP	LDA	DX
	CAS	DY
	JMP	XGTY	DX GREATER DY
YGTX	NOP		DY GREATER OR EQUAL DX
	LDA	STPY
	STA	STPL
	LDA	STPX
	STA	STPS
	LDA	DX
	STA	DS
	LDA	DY
	STA	DL
	JMP	GTE
*
XGTY	LDA	STPY
	STA	STPS
	LDA	STPX
	STA	STPL
	LDA	DX
	STA	DL
	LDA	DY
	STA	DS	
*	
GTE	LDA	DL	LONG DISTANCE
	LGR	1	DIVIDE BY TWO
	STA	ERR	INITIALIZE ERROR COUNTER
*
*
*	
LOOP	LDA	DL
	SNZ
	JMP	FNSH	END OF WORK - HOPE SO....
	SUB	=1	DECREMENT DL
	STA	DL
	LDA	ERR
	SUB	DS
	STA	ERR
	SMI		SKIP IF NOT OVERFLOWN (MINUS)
	JMP	NDIA	NO DIAG STEP
	ADD	DL	RELOAD
	STA	ERR
	LDA	DS
	SUB	=1
	STA	DS
	JST*	STPD
	JMP	STEN	END OF STEP
NDIA	JST*	STPL	LONG DIR STEP ONLY
STEN	JMP	LOOP	RELOOP
*
FNSH	LDA	XN
	STA	X
	LDA	YN
	STA	Y
	JMP*	MOVE	END OF THE ROUTINE
**********************
*	
*			VARIABLES
*
X	DEC	0	PEN POSITION, X VALUE
Y	DEC	0	PEN POSITION, Y VALUE
XN	DEC	0	NEW PEN POSITION, X VALUE
YN	DEC	0	NEW PEN POSITION, Y VALUE
DX	DEC	0	X DIFFERENCE TO GO
DY	DEC	0	Y DIFFERENCE TO GO
*
DL	DEC	0	LONG DISTANCE NEGATIVE
DS	DEC	0	SHORT DISTANCE NEGATIVE
STPL	DAC	**	ROUTINE TO LONG DISTANCE STEP
STPS	DAC	**	ROUTINE TO SHORT DISTANCE STEP
STPD	DAC	**	ROUTINE TO DIAGONAL STEP
ERR	DEC	0	ERROR COUNTER
*
STPX	DAC	**	X STEP ROUTINE
STPY	DAC	**	Y STEP ROUTINE
DIYP	DAC	**	DIAGONAL X-DIR+UP STEP ROUTINE
DIYN	DAC	**	DIAGONAL X-DIR+DOWN STEP ROUTINE
TMP	DAC	**	UNIVERSAL POINTER
*
*			GLUE IN THE MOVEMENT
MU	XAC	PL$U
MD	XAC	PL$D
ML	XAC	PL$L
MR	XAC	PL$R
MUL	XAC	PL$UL
MUR	XAC	PL$UR
MDL	XAC	PL$DL
MDR	XAC	PL$DR
*
*
	END