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382 lines
7.6 KiB
ArmAsm
382 lines
7.6 KiB
ArmAsm
;
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; Extended memory driver for the VDC RAM available on all C128 machines
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; (based on code by Ullrich von Bassewitz)
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; Maciej 'YTM/Elysium' Witkowiak <ytm@elysium.pl>
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; 06,20.12.2002
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.include "zeropage.inc"
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.include "em-kernel.inc"
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.include "em-error.inc"
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.macpack generic
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; ------------------------------------------------------------------------
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; Header. Includes jump table
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.segment "JUMPTABLE"
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; Driver signature
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.byte $65, $6d, $64 ; "emd"
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.byte $00 ; EM API version number
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; Jump table.
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.word INSTALL
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.word DEINSTALL
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.word PAGECOUNT
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.word MAP
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.word USE
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.word COMMIT
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.word COPYFROM
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.word COPYTO
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; ------------------------------------------------------------------------
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; Constants
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VDC_ADDR_REG = $D600 ; VDC address
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VDC_DATA_REG = $D601 ; VDC data
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VDC_DATA_HI = 18 ; used registers
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VDC_DATA_LO = 19
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VDC_CSET = 28
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VDC_DATA = 31
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; ------------------------------------------------------------------------
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; Data.
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.data
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pagecount: .word 64 ; $0000-$3fff as 16k default
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curpage: .word $ffff ; currently mapped-in page (invalid)
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.bss
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window: .res 256 ; memory window
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.code
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; ------------------------------------------------------------------------
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; INSTALL routine. Is called after the driver is loaded into memory. If
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; possible, check if the hardware is present and determine the amount of
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; memory available.
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; Must return an EM_ERR_xx code in a/x.
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;
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INSTALL:
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; do test for VDC presence here???
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ldx #VDC_CSET ; determine size of RAM...
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jsr vdcgetreg
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sta tmp1
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ora #%00010000
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jsr vdcputreg ; turn on 64k
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jsr settestadr1 ; save original value of test byte
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jsr vdcgetbyte
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sta tmp2
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lda #$55 ; write $55 here
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ldy #ptr1
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jsr test64k ; read it here and there
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lda #$aa ; write $aa here
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ldy #ptr2
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jsr test64k ; read it here and there
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jsr settestadr1
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lda tmp2
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jsr vdcputbyte ; restore original value of test byte
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lda ptr1 ; do bytes match?
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cmp ptr1+1
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bne @have64k
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lda ptr2
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cmp ptr2+1
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bne @have64k
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ldx #VDC_CSET
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lda tmp1
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jsr vdcputreg ; restore 16/64k flag
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jmp @endok ; and leave default values for 16k
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@have64k:
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lda #<256
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ldx #>256
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sta pagecount
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stx pagecount+1
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@endok:
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lda #<EM_ERR_OK
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ldx #>EM_ERR_OK
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rts
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test64k:
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sta tmp1
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sty ptr3
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lda #0
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sta ptr3+1
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jsr settestadr1
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lda tmp1
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jsr vdcputbyte ; write $55
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jsr settestadr1
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jsr vdcgetbyte ; read here
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pha
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jsr settestadr2
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jsr vdcgetbyte ; and there
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ldy #1
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sta (ptr3),y
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pla
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dey
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sta (ptr3),y
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rts
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settestadr1:
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ldy #$02 ; test page 2 (here)
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.byte $2c
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settestadr2:
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ldy #$42 ; or page 64+2 (there)
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lda #0
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jmp vdcsetsrcaddr
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; ------------------------------------------------------------------------
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; DEINSTALL routine. Is called before the driver is removed from memory.
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; Can do cleanup or whatever. Must not return anything.
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;
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DEINSTALL:
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;on C128 restore font and clear the screen?
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rts
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; ------------------------------------------------------------------------
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; PAGECOUNT: Return the total number of available pages in a/x.
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;
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PAGECOUNT:
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lda pagecount
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ldx pagecount+1
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rts
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; ------------------------------------------------------------------------
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; MAP: Map the page in a/x into memory and return a pointer to the page in
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; a/x. The contents of the currently mapped page (if any) may be discarded
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; by the driver.
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;
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MAP: sta curpage
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stx curpage+1
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sta ptr1+1
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ldy #0
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sty ptr1
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lda #<window
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sta ptr2
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lda #>window
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sta ptr2+1
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jsr transferin
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lda #<window
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ldx #>window
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rts
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; copy a single page from (ptr1):VDCRAM to (ptr2):RAM
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transferin:
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lda ptr1
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ldy ptr1+1
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jsr vdcsetsrcaddr ; set source address in VDC
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ldy #0
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ldx #VDC_DATA
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stx VDC_ADDR_REG
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@L0: bit VDC_ADDR_REG
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bpl @L0
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lda VDC_DATA_REG ; get 2 bytes at a time to speed-up
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sta (ptr2),y ; (in fact up to 8 bytes could be fetched with special VDC config)
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iny
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lda VDC_DATA_REG
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sta (ptr2),y
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iny
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bne @L0
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rts
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; ------------------------------------------------------------------------
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; USE: Tell the driver that the window is now associated with a given page.
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USE: sta curpage
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stx curpage+1 ; Remember the page
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lda #<window
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ldx #>window ; Return the window
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done: rts
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; ------------------------------------------------------------------------
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; COMMIT: Commit changes in the memory window to extended storage.
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COMMIT:
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lda curpage ; jump if no page mapped
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ldx curpage+1
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bmi done
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sta ptr1+1
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ldy #0
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sty ptr1
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lda #<window
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sta ptr2
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lda #>window
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sta ptr2+1
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; fall through to transferout
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; copy a single page from (ptr2):RAM to (ptr1):VDCRAM
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transferout:
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lda ptr1
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ldy ptr1+1
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jsr vdcsetsrcaddr ; set source address in VDC
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ldy #0
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ldx #VDC_DATA
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stx VDC_ADDR_REG
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@L0: bit VDC_ADDR_REG
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bpl @L0
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lda (ptr2),y ; speedup does not work for writing
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sta VDC_DATA_REG
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iny
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bne @L0
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rts
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; ------------------------------------------------------------------------
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; COPYFROM: Copy from extended into linear memory. A pointer to a structure
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; describing the request is passed in a/x.
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; The function must not return anything.
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;
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COPYFROM:
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jsr setup
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beq @L2 ; Skip if no full pages
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; Copy full pages
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@L1: jsr transferin
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inc ptr1+1
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inc ptr2+1
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dec tmp1
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bne @L1
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; Copy the remainder of the page
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@L2: ldy #EM_COPY_COUNT
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lda (ptr3),y ; Get bytes in last page
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beq @L4
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sta tmp1
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; Transfer the bytes in the last page
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ldy #0
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@L3: jsr vdcgetbyte
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sta (ptr2),y
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iny
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dec tmp1
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lda tmp1
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bne @L3
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@L4: rts
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; ------------------------------------------------------------------------
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; COPYTO: Copy from linear into extended memory. A pointer to a structure
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; describing the request is passed in a/x.
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; The function must not return anything.
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;
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COPYTO:
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jsr setup
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beq @L2 ; Skip if no full pages
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; Copy full pages
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@L1: jsr transferout
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inc ptr1+1
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inc ptr2+1
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dec tmp1
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bne @L1
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; Copy the remainder of the page
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@L2: ldy #EM_COPY_COUNT
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lda (ptr3),y ; Get bytes in last page
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beq @L4
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sta tmp1
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; Transfer the bytes in the last page
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ldy #0
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@L3: lda (ptr2),y
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jsr vdcputbyte
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iny
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dec tmp1
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lda tmp1
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bne @L3
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@L4: rts
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;-------------------------------------------------------------------------
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; Helper functions to handle VDC ram
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;
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vdcsetsrcaddr:
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ldx #VDC_DATA_LO
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stx VDC_ADDR_REG
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@L0: bit VDC_ADDR_REG
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bpl @L0
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sta VDC_DATA_REG
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dex
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tya
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stx VDC_ADDR_REG
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sta VDC_DATA_REG
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rts
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vdcgetbyte:
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ldx #VDC_DATA
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vdcgetreg:
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stx VDC_ADDR_REG
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@L0: bit VDC_ADDR_REG
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bpl @L0
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lda VDC_DATA_REG
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rts
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vdcputbyte:
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ldx #VDC_DATA
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vdcputreg:
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stx VDC_ADDR_REG
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@L0: bit VDC_ADDR_REG
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bpl @L0
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sta VDC_DATA_REG
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rts
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; ------------------------------------------------------------------------
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; Helper function for COPYFROM and COPYTO: Store the pointer to the request
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; structure and prepare data for the copy
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;
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setup:
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sta ptr3
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stx ptr3+1 ; Save the passed em_copy pointer
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ldy #EM_COPY_OFFS
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lda (ptr3),y
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sta ptr1
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ldy #EM_COPY_PAGE
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lda (ptr3),y
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sta ptr1+1 ; From
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ldy #EM_COPY_BUF
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lda (ptr3),y
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sta ptr2
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iny
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lda (ptr3),y
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sta ptr2+1 ; To
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ldy #EM_COPY_COUNT+1
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lda (ptr3),y ; Get number of pages
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sta tmp1
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rts
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