;
; Extended memory driver for the Apple II language card
;
; Stefan Haubenthal, 2003-12-13
; Ullrich von Bassewitz, 2002-12-02,2003-12-21
;

	.include	"zeropage.inc"

	.include	"em-kernel.inc"
	.include	"em-error.inc"


	.macpack	generic


; ------------------------------------------------------------------------
; Header. Includes jump table

.segment	"JUMPTABLE"

; Driver signature

	.byte	$65, $6D, $64		; "emd"
       	.byte  	EMD_API_VERSION         ; EM API version number

; Jump table.

	.word	INSTALL
	.word	UNINSTALL
	.word	PAGECOUNT
	.word	MAP
	.word	USE
	.word	COMMIT
	.word	COPYFROM
	.word	COPYTO

; ------------------------------------------------------------------------
; Constants

BASE	= $D000				; $Cxxx -> $Dxxx bank 1
BASE2	= $D000
PAGES	= ($10000 - BASE) / 256
ROMONLY2= $C082
LC2RW	= $C083
LC1RW	= $C08B

; ------------------------------------------------------------------------
; Data.

.bss
curpage:       	.res    1               ; Current page number

.bss
window:		.res	256		; Memory "window"

.code

; ------------------------------------------------------------------------
; INSTALL routine. Is called after the driver is loaded into memory. If
; possible, check if the hardware is present and determine the amount of
; memory available.
; Must return an EM_ERR_xx code in a/x.
;

INSTALL:
        lda     #$FF
        sta     curpage                 ; Invalidate the current page
	lda	#EM_ERR_OK
	ldx	#$00
;  	rts                             ; Run into UNINSTALL instead

; ------------------------------------------------------------------------
; UNINSTALL routine. Is called before the driver is removed from memory.
; Can do cleanup or whatever. Must not return anything.
;

UNINSTALL:
	rts


; ------------------------------------------------------------------------
; PAGECOUNT: Return the total number of available pages in a/x.
;

PAGECOUNT:
	lda	#<PAGES
	ldx	#>PAGES
	rts

; ------------------------------------------------------------------------
; MAP: Map the page in a/x into memory and return a pointer to the page in
; a/x. The contents of the currently mapped page (if any) may be discarded
; by the driver.
;

MAP:	sta	curpage			; Remember the new page

	add	#>BASE
	sta	ptr1+1
	ldy	#$00
	sty	ptr1

	lda	#<window
	sta	ptr2
	lda	#>window
	sta	ptr2+1

; Transfer one page

	jsr	transfer		; Transfer one page

; Return the memory window

	lda	#<window
	ldx	#>window		; Return the window address
	rts

; ------------------------------------------------------------------------
; USE: Tell the driver that the window is now associated with a given page.

USE:	sta	curpage			; Remember the page
	lda	#<window
	ldx	#>window		; Return the window
	rts

; ------------------------------------------------------------------------
; COMMIT: Commit changes in the memory window to extended storage.

COMMIT: lda	curpage			; Get the current page
	bmi	done			; Jump if no page mapped

	add	#>BASE
	sta	ptr2+1
	ldy	#$00
	sty	ptr2

	lda	#<window
	sta	ptr1
	lda	#>window
	sta	ptr1+1

; Transfer one page. Y must be zero on entry

transfer:
	ldx	#$00
	lda	ptr2+1
	cmp	#>BASE
	bcc	@L1
	cmp	#>BASE2
	bcs	@L1
	adc	#>(BASE2-BASE)
	sta	ptr2+1
	ldx	#LC1RW-LC2RW
@L1:	lda	ptr1+1
	cmp	#>BASE
	bcc	@L2
	cmp	#>BASE2
	bcs	@L2
	adc	#>(BASE2-BASE)
	sta	ptr1+1
	ldx	#LC1RW-LC2RW
@L2:	sei
	lda	LC2RW,x			; Bank out ROMs
	lda	LC2RW,x

; Unroll the following loop

loop:	.repeat	8
	lda	(ptr1),y
	sta	(ptr2),y
	iny
	.endrep

	bne	loop

; Restore the old memory configuration, allow interrupts

	lda	ROMONLY2		; Bank in ROMs
	cli

; Done

done:	rts

; ------------------------------------------------------------------------
; COPYFROM: Copy from extended into linear memory. A pointer to a structure
; describing the request is passed in a/x.
; The function must not return anything.
;

COPYFROM:
	sta	ptr3
	stx	ptr3+1			; Save the passed em_copy pointer

	ldy	#EM_COPY::OFFS
	lda	(ptr3),y
	sta	ptr1
	ldy	#EM_COPY::PAGE
	lda	(ptr3),y
	add	#>BASE
	sta	ptr1+1			; From

	ldy	#EM_COPY::BUF
	lda	(ptr3),y
	sta	ptr2
	iny
	lda	(ptr3),y
	sta	ptr2+1			; To

common: ldy	#EM_COPY::COUNT+1
	lda	(ptr3),y		; Get number of pages
	beq	@L2			; Skip if no full pages
	sta	tmp1

; Copy full pages allowing interrupts after each page copied

	ldy	#$00
@L1:	jsr	transfer
	inc	ptr1+1
	inc	ptr2+1
	dec	tmp1
	bne	@L1

; Copy the remainder of the page

@L2:	ldy	#EM_COPY::COUNT
	lda	(ptr3),y		; Get bytes in last page
	beq	@L4
	pha

	sei
	lda	LC2RW,x			; Bank out ROMs
	lda	LC2RW,x
	pla
	tax

; Transfer the bytes in the last page

	ldy	#$00
@L3:	lda	(ptr1),y
	sta	(ptr2),y
	iny
	dex
	bne	@L3

; Restore the old memory configuration, allow interrupts

	lda	ROMONLY2		; Bank in ROMs
	cli

; Done

@L4:	rts

; ------------------------------------------------------------------------
; COPYTO: Copy from linear into extended memory. A pointer to a structure
; describing the request is passed in a/x.
; The function must not return anything.
;

COPYTO: sta	ptr3
	stx	ptr3+1			; Save the passed em_copy pointer

	ldy	#EM_COPY::OFFS
	lda	(ptr3),y
	sta	ptr2
	ldy	#EM_COPY::PAGE
	lda	(ptr3),y
	add	#>BASE
	sta	ptr2+1			; To

	ldy	#EM_COPY::BUF
	lda	(ptr3),y
	sta	ptr1
	iny
	lda	(ptr3),y
	sta	ptr1+1			; From

	jmp	common