SBTTL 'Character/Attribute Memory Routines (27_Nov_84)'
	PAGE
;======================================================================
;
;	Copyright 1984
;	Morrow Designs, Inc.
;	San Leandro, Ca.
;
;----------------------------------------------------------------------
; Index (27_Nov_84)
;------------------
;
;	SETCUR	Set the Cursor Position
;	SETPOS	Figure the Screen Position
;	LINBAS	Calculate the Line Base
;	CLREOLA	Clear to the End of a Line
;	CLEAR	Clear Line Primative
;	OUTCHR	Output a Character to the Screen
;	WRATT	Write an Attribute
;
;	CALCD	Calculate Destination Address
;	CALCATT	Calculate Attribute
;	CALCS	Calculate Source Address
;	CALCATT2	Calculate Attribute 2
;	SETSD	Set the Source and Destination Pointers
;
;	INSMOVE	Move characters, and attribute nibbles for Char/Line Insert
;	DELMOVE	Move characters, and attribute nibbles for Char/Line Delete
	PAGE

;----------------------------------------------------------------------
; Set the Cursor Position (21_Nov_84)
;------------------------------------
;
SETCUR:	LDA	ROW		;A:= Current Row
	JSR	LINBAS		;Set LB to Starting Address of Current Line

; Figure the Screen Position
;---------------------------
;
SETPOS:	CLC
	LDA	LB
	ADC	COLMN		;A:= Low Byte Cursor Address
	LDX	#15		;X:= Cursor Address Register Index (Lo_Byte)
	STX	CRTC		;Select Lo_Byte of the Cursor Adress Register
	STA	CRTC+1		;Install the Low Byte of the Cursor Address

	LDA	TEMP		;(Set in LINBAS to un-truncated Hi_Byte Addr)
	ADC	#0		;A:= High Byte Cursor Address
	DEX			;X:= Cursor Address Register Index (Hi_Byte)
	STX	CRTC		;Select Hi_Byte of the Cursor Adress Register
	STA	CRTC+1		;Install the Hi Byte of the Cursor Address
	RTS			;Return

;----------------------------------------------------------------------
; Calculate the Line Base (21_Nov_84)
;------------------------------------
;	1) Enter this routine with the accm equal to the desired row. The
;	   routine sets LB (Low_Byte) and LB+1 (High_Byte) to the absolute
;	   starting address of the row.
;
LINBAS:	ASL	A
	TAX			;X:= Row * 2
	LDA	LINES,X
	CLC
	ADC	SCBASE		;A:= Low Byte of Absolute Screen Address
	STA	LB		;LB:= Low Byte Address (same for CRAM & ARAM)

	LDA	LINES+1,X
	ADC	SCBASE+1	;A:= High Byte of Absolute Screen Address
	STA	TEMP		;(Save Address for Cursor Positioning)

	AND	#%111		;Truncate to less than 2K
	ORA	#HIGH CRAM	;Compute high byte of CRAM Line base
	STA	LB+1		;LB+1:= High Byte Address
	RTS			;Return
	PAGE

;----------------------------------------------------------------------
; Clear Line Primitive (27_Nov_84)
;---------------------------------
;
CLEOLA:	EOR	#$FF
	SEC
 	ADC	#80
	TAX

CLEAR:	LDY	#79
CLLP1:	LDA	#' '
	STA	(LB),Y
	LDA	ATTTAB+0
	JSR	WRATT
	DEY
	DEX
	BNE	CLLP1

	RTS
	PAGE

;----------------------------------------------------------------------
; Output a Character to the Screen
;---------------------------------
;	1) On Entry:
;		X = current attribute being set
;		A = character to display
;
OUTCHR:	JSR	XLTIN		; translate input char if req'd
	LDY	COLMN
	STA	(LB),Y		; put char on screen
	TXA
	JSR	WRATT		; set it's attribute
	INY
	CPY	#80		; see if auto LF req'd
	BNE	OUTSK1		; if not, just set column for next char

	LDA	#0		; else, set column 0
	STA	COLMN
	JMP	LF		; and perform a line feed

OUTSK1:	STY	COLMN
	RTS

;----------------------------------------------------------------------
; Write an Attribute
;-------------------
;
WRATT:	STA	TEMPATT		; save attribute value
	TYA
	PHA			; save character index
	JSR	CALCATT		; calculate address for attribute 
	LDY	#0
	LDA	TEMPATT		; get back attribute
	STA	(ATTRD),Y	; write attribute back out
	PLA
	TAY
	RTS
	PAGE

;----------------------------------------------------------------------
; Calculate Destination Address
;------------------------------
;
CALCD:	PHA
	CLC			; calculate destination address for character move
	ADC	LB
	STA	CHARD
	LDA	#0
	ADC	LB+1
	AND	#%00110111	; wrap around for 2000 - 27FF address range
	STA	CHARD+1
	PLA


; Calculate Attribute (21_Nov_84)
;--------------------------------
;
CALCATT:CLC			;16 bit add of LB and Y reg
	ADC	LB
	STA	ATTRD		;ATTRD:= Lo_Byte of Attribute Address
	LDA	#0
	ADC	LB+1
	AND	#%00000111	;Truncate to 2k
	ORA	#HIGH ARAM	;Or in the Base Address of the Attribute Ram
	STA	ATTRD+1		;ATTRD+1:= Hi_Byte of Attribute Address
	RTS			;Return
	PAGE

;----------------------------------------------------------------------
; Calculate Source Address of Character Move
;-------------------------------------------
;
CALCS:	PHA
	CLC			; calculate source address for character move
	ADC	LB2
	STA	CHARS
	LDA	#0
	ADC	LB2+1
	AND	#%00110111	; wrap around for 2000 - 27FF address range
	STA	CHARS+1
	PLA


; Calculate Source Address of Attribute Move (21_Nov_84)
;-------------------------------------------------------
;
CALCATT2:
	CLC			; 16 bit add of LB and Y reg
	ADC	LB2
	STA	ATTRS		;ATTRS:= Lo_Byte of Attribute Address
	LDA	#0
	ADC	LB2+1
	AND	#%00000111	;Truncate to 2k
	ORA	#HIGH ARAM	;Or in the Attribute Ram Base Address
	STA	ATTRS+1		;ATTRS+1:= Hi_Byte of Attribute Address
	RTS
	PAGE

;----------------------------------------------------------------------
; Set the Source and Destination Pointers
;----------------------------------------
;
SETSD:	LDA	LB		; set up character destination pointer
	STA	CHARD
	LDA	LB+1
	STA	CHARD+1
	LDA	LB2		; and source pointer
	STA	CHARS
	LDA	LB2+1
	STA	CHARS+1
	RTS
	PAGE

;----------------------------------------------------------------------
; Move Characters/Attributes for Char/Line Insert (21_Nov_84)
;------------------------------------------------------------
;	1) On entry:
;		CHARS	Source (absolute address) of Characters in CRAM
;		ATTRS	   "       "        "     "  Attributes in ARAM
;		CHARD	Destination (absolute address) of Characters in CRAM
;		ATTRD	   "            "        "     "  Attributes in ARAM
;		TRANSFR	Count of the number of Attributes to move
;
INSMOVE:LDY	#0		;Y_Index:= 0 (for absolute indirect)

IMLP1:	LDA	(ATTRS),Y	;Loop
	STA	(ATTRD),Y	;	Move an Attribute

	LDA	(CHARS),Y
	STA	(CHARD),Y	;	Move a Character

	DEC	TRANSFR		;	Decrement the Byte Count
	LDA	#$0FF
	CMP	TRANSFR
	BNE	IMSK0		;	If (Lo_Byte of Count eq 0FFh)

	DEC	TRANSFR+1	;		If (Hi_Byte - 1 eq 0)
	BMI	IMSK2		;			Break

IMSK0:	DEC	CHARS		;	Dec (Lo) Source Pointers
	DEC	ATTRS
	LDA	#$FF		;	If (Source Pointers eq 0FF)
	CMP	ATTRS
	BNE	IMSK1

	DEC	CHARS+1		;		Dec (Hi) Source Pointers
	DEC	ATTRS+1
	LDA	#7		;		If (Address ready to Wrap)
	CMP	ATTRS+1
	BNE	IMSK1

	LDA	#0FH
	STA	ATTRS+1	;			Reset Hi_Byte Attribute
	LDA	#$2F
	STA	CHARS+1		;			Reset Hi_Byte Character

IMSK1:	DEC	CHARD		;	Dec (Lo) Destination Pointers
	DEC	ATTRD
	LDA	#$FF		;	If (Destination Pointers eq 0FF)
	CMP	ATTRD
	BNE	IMLP1

	DEC	CHARD+1		;		Dec (Hi) Destination Pointers
	DEC	ATTRD+1
	LDA	#7		;		If (Address Ready to Wrap)
	CMP	ATTRD+1
	BNE	IMLP1

	LDA	#0FH
	STA	ATTRD+1
	LDA	#$2F
	STA	CHARD+1		;			Reset Hi_Byte Pointers
	JMP	IMLP1

IMSK2:	RTS			;Return
	PAGE

;----------------------------------------------------------------------
; Move Characters/Attribute for Char/Line Delete (21_Nov_84)
;-----------------------------------------------------------
;	1) On entry:
;		CHARS	Source (absolute address) of Characters in CRAM
;		ATTRS	   "       "        "     "  Attributes in ARAM
;		CHARD	Destination (absolute address) of Characters in CRAM
;		ATTRD	   "            "        "     "  Attributes in ARAM
;		TRANSFR	Count of the number of Attributes to move
;
DELMOVE:LDY	#0		;Y_Index:= 0 (for absolute indirect)

DMLP1:	LDA	(ATTRS),Y	;Loop
	STA	(ATTRD),Y	;	Move an Attribute

	LDA	(CHARS),Y
	STA	(CHARD),Y	;	Move a Character

	DEC	TRANSFR		;	Decrement the Byte Count
	LDA	#$0FF
	CMP	TRANSFR
	BNE	DMSK0		;	If (Lo_Byte of Count eq 0FFh)

	DEC	TRANSFR+1	;		If (Hi_Byte - 1 eq 0FFh)
	BMI	DMSK2		;			Break

DMSK0:	INC	CHARS		;	Inc (Lo) Source Pointers
	INC	ATTRS
	BNE	DMSK1		;	If (Souce Pointers eq 0)

	INC	CHARS+1		;		Inc (Hi) Source Pointers
	INC	ATTRS+1
	LDA	#$10		;		If (Pointers Ready to Wrap)
	CMP	ATTRS+1
	BNE	DMSK1

	LDA	#8		;			Reset Hi Pointers
	STA	ATTRS+1
	LDA	#$28
	STA	CHARS+1

DMSK1:	INC	CHARD		;	Inc (Lo) Destination Pointers
	INC	ATTRD
	BNE	DMLP1		;	If (Destination Pointers eq 0)

	INC	CHARD+1		;		Inc (Hi) Destination Pointers
	INC	ATTRD+1
	LDA	#$10		;		If (Pointers Ready to Wrap)
	CMP	ATTRD+1
	BNE	DMLP1

	LDA	#8
	STA	ATTRD+1
	LDA	#$28
	STA	CHARD+1		;			Reset Hi Pointers
	JMP	DMLP1

DMSK2:	RTS			;Return

	END