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2c975d3642
Up to now static drivers were created via co65 from dynamic drivers. However there was an issue with that approach: The dynamic drivers are "o65 simple files" which obligates that they start with the 'code' segment. However dynamic drivers need to start with the module header - which is written to. For dynamic drivers this isn't more than a conceptual issue because they are always contain a 'data' segment and may therefore only be loaded into writable memory. However when dynamic drivers are converted to static drivers using co65 then that issue becomes a real problem as then the 'code' segment may end up in non-writable memory - and thus writing to the module header fails. Instead of changing the way dynamic drivers work I opted to rather make static driver creation totally independent from dynamic drivers. This allows to place the module header in the 'data' segment (see 'module.mac').
329 lines
7.1 KiB
ArmAsm
329 lines
7.1 KiB
ArmAsm
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; Extended memory driver for the CBM510 additional RAM banks. Driver works
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; without problems when linked statically.
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;
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; Ullrich von Bassewitz, 2002-12-09, 2003-12-27
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;
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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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.include "cbm510.inc"
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.macpack generic
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.macpack module
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; ------------------------------------------------------------------------
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; Header. Includes jump table
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module_header _cbm510_ram_emd
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; Driver signature
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.byte $65, $6d, $64 ; "emd"
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.byte EMD_API_VERSION ; EM API version number
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; Library reference
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.addr $0000
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; Jump table
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.addr INSTALL
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.addr UNINSTALL
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.addr PAGECOUNT
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.addr MAP
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.addr USE
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.addr COMMIT
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.addr COPYFROM
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.addr COPYTO
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; ------------------------------------------------------------------------
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; Constants
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RAMBANK = 1
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OFFS = 2
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; ------------------------------------------------------------------------
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; Data.
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.bss
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curpage: .res 1 ; Current page number
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window: .res 256 ; Memory "window"
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pagecount: .res 1 ; Number of available pages
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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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lda #$FF
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sta curpage ; Invalidate the current page
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sta pagecount ; Assume all memory available
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sec
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jsr $FF99 ; MEMTOP
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cmp #RAMBANK ; Top of memory in bank 2?
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bne @L1 ; No: We can use all the memory
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txa
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sub #OFFS
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tya
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sbc #$00
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sta pagecount
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@L1: lda #<EM_ERR_OK
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ldx #>EM_ERR_OK
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; rts ; Run into UNINSTALL instead
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; ------------------------------------------------------------------------
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; UNINSTALL 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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UNINSTALL:
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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 #0
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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 ; Remember the new page
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sta ptr1+1
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lda #OFFS
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sta ptr1
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; Transfer one page
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ldx IndReg
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lda #RAMBANK
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sta IndReg
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ldy #$00
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@L1: .repeat 2
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lda (ptr1),y
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sta window,y
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iny
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.endrepeat
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bne @L1
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stx IndReg
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; Return the memory window
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lda #<window
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ldx #>window ; Return the window address
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rts
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; ------------------------------------------------------------------------
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; USE: Tell the driver that the window is now associated with a given page.
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USE: sta curpage ; Remember the page
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lda #<window
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ldx #>window ; Return the window
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rts
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; ------------------------------------------------------------------------
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; COMMIT: Commit changes in the memory window to extended storage.
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COMMIT: lda curpage ; Get the current page
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cmp #$FF
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beq done ; Jump if no page mapped
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sta ptr1+1
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lda #OFFS
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sta ptr1
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; Transfer one page
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ldx IndReg
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lda #RAMBANK
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sta IndReg
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ldy #$00
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@L1: .repeat 2
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lda window,y
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sta (ptr1),y
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iny
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.endrepeat
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bne @L1
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stx IndReg
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; Done
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done: 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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; Setup the buffer address in this bank.
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sta copyfrom_buf
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stx copyfrom_buf+1
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; Check if we must copy full pages
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ldx ptr2+1
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beq @L2
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; Copy full pages
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ldx #$00
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@L1: jsr copyfrom
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inc ptr1+1
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inc copyfrom_buf+1
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@L2: dec ptr2+1
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bne @L1
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; Copy the remaining page
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ldx ptr2
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beq @L3
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jsr copyfrom
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; Restore the indirect segment
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@L3: lda ExecReg
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sta IndReg
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; Done
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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: jsr setup
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; Setup the buffer address in this bank.
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sta copyto_buf
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stx copyto_buf+1
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; Check if we must copy full pages
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ldx ptr2+1
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beq @L2
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; Copy full pages
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ldx #$00
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@L1: jsr copyto
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inc ptr1+1
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inc copyto_buf+1
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@L2: dec ptr2+1
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bne @L1
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; Copy the remaining page
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ldx ptr2
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beq @L3
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jsr copyto
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; Restore the indirect segment
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@L3: lda ExecReg
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sta IndReg
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; Done
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rts
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; ------------------------------------------------------------------------
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; setup: Helper function for COPYFROM and COPYTO, will setup parameters.
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;
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setup: 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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add #OFFS
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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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adc #$00
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sta ptr1+1
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ldy #EM_COPY::COUNT
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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 ; Get count into ptr2
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ldy #EM_COPY::BUF+1
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lda (ptr3),y
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tax
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dey
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lda (ptr3),y ; Get the buffer pointer into a/x
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ldy #RAMBANK
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sty IndReg
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ldy #$00
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rts
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; ------------------------------------------------------------------------
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; copyfrom
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.data
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copyfrom:
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lda (ptr1),y
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copyfrom_buf = * + 1
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sta $0000,y
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iny
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dex
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bne copyfrom
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rts
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; ------------------------------------------------------------------------
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; copyto
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.data
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copyto:
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copyto_buf = * + 1
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lda $0000,y
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sta (ptr1),y
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iny
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dex
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bne copyto
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rts
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