--- /dev/null
+;
+; Extended memory driver for the Apple II auxiliary memory
+;
+; Stefan Haubenthal, 2003-12-12
+; Ullrich von Bassewitz, 2002-12-02
+;
+
+ .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 DEINSTALL
+ .word PAGECOUNT
+ .word MAP
+ .word USE
+ .word COMMIT
+ .word COPYFROM
+ .word COPYTO
+
+; ------------------------------------------------------------------------
+; Constants
+
+BASE = $0200
+AUXCARD = $C30C ; Card signature
+AUXMOVE = $C311 ; Auxiliary move routine
+PAGES = ($C000 - BASE) / 256
+
+; ------------------------------------------------------------------------
+; Data.
+
+.data
+curpage: .byte $FF ; Current page number (invalid)
+
+.bss
+window: .res 256 ; Memory "window"
+
+.code
+
+; ------------------------------------------------------------------------
+; INSTALL routine. Is called after the driver is loaded into memory. If
+; possible, check if the hardware is present and determine the amount of
+; memory available.
+; Must return an EM_ERR_xx code in a/x.
+;
+
+INSTALL:
+ ldx #0
+ lda AUXCARD
+ and #$f0
+ cmp #$80
+ bne @L1
+ lda #EM_ERR_OK
+ rts
+@L1: lda #EM_ERR_NO_DEVICE
+; rts
+
+; ------------------------------------------------------------------------
+; DEINSTALL routine. Is called before the driver is removed from memory.
+; Can do cleanup or whatever. Must not return anything.
+;
+
+DEINSTALL:
+ 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 #$00
+ sty ptr1
+
+ lda #<window
+ sta ptr2
+ lda #>window
+ sta ptr2+1
+
+; Transfer one page
+
+ clc ; Direction flag
+ jsr transfer ; Transfer one page
+
+; Return the memory window
+
+ lda #<window
+ ldx #>window ; Return the window address
+
+; Done
+
+done: rts
+
+; ------------------------------------------------------------------------
+; USE: Tell the driver that the window is now associated with a given page.
+
+USE: sta curpage ; Remember the page
+ lda #<window
+ ldx #>window ; Return the window
+ rts
+
+; ------------------------------------------------------------------------
+; COMMIT: Commit changes in the memory window to extended storage.
+
+COMMIT: lda curpage ; Get the current page
+ cmp #$FF
+ beq done ; Jump if no page mapped
+
+ add #>BASE
+ sta ptr2+1
+ ldy #$00
+ sty ptr2
+
+ lda #<window
+ sta ptr1
+ lda #>window
+ sta ptr1+1
+ lda #<$FF
+ sta ptr4
+ lda #>$FF
+ sta ptr4+1
+ sec ; Direction flag
+
+; Transfer one page/all bytes
+
+transfer:
+ php
+ lda ptr1
+ sta $3C
+ add ptr4
+ sta $3E
+ lda ptr1+1
+ sta $3D
+ adc ptr4+1
+ sta $3F
+ lda ptr2
+ sta $42
+ lda ptr2+1
+ sta $43
+ plp
+ jmp AUXMOVE
+
+; ------------------------------------------------------------------------
+; 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
+ clc ; Direction flag
+
+common: ldy #EM_COPY::COUNT
+ lda (ptr3),y ; Get bytes in last page
+ sta ptr4
+ iny
+ lda (ptr3),y ; Get number of pages
+ sta ptr4+1
+
+ jmp transfer
+
+; ------------------------------------------------------------------------
+; 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
+
+ sec ; Direction flag
+ jmp common
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