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https://github.com/cc65/cc65.git
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321 lines
6.8 KiB
ArmAsm
321 lines
6.8 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 !!! UNTESTED !!!
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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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; ------------------------------------------------------------------------
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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 UNINSTALL
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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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RAMBANK = 2
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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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ldx UsrMemTop+2
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cpx #RAMBANK ; Top of memory in bank 2?
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bne @L1 ; No: We can use all the memory
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clc
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adc UsrMemTop+1
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@L1: sta pagecount
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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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; ------------------------------------------------------------------------
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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 #$00
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@L1: lda (ptr1),y
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sta window,y
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iny
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lda (ptr1),y
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sta window,y
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iny
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bne @L1
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stx IndReg
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; Return the memory window
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lda #<window
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ldx #>window ; Return the window address
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rts
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; ------------------------------------------------------------------------
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; USE: Tell the driver that the window is now associated with a given page.
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USE: sta curpage ; Remember the page
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lda #<window
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ldx #>window ; Return the window
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rts
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; ------------------------------------------------------------------------
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; COMMIT: Commit changes in the memory window to extended storage.
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COMMIT: lda curpage ; Get the current page
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cmp #$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: lda window,y
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sta (ptr1),y
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iny
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lda window,y
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sta (ptr1),y
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iny
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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 (ptr1),y
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tax
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dey
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lda (ptr1),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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