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https://github.com/cc65/cc65.git
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b3ed17f575
Note: These drivers are currently untested because I didn't realize that using the drivers would need file routines, which are not available right now. So in fact the drivers are not only untested, they are also unusable on the target platforms, because they cannot be loaded. git-svn-id: svn://svn.cc65.org/cc65/trunk@1732 b7a2c559-68d2-44c3-8de9-860c34a00d81
320 lines
6.7 KiB
ArmAsm
320 lines
6.7 KiB
ArmAsm
;
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; Extended memory driver for the CBM510 additional RAM banks
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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 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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RAMBANK = 2
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OFFS = 2
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; ------------------------------------------------------------------------
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; Data.
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.data
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curpage: .byte $FF ; Current page number (invalid)
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.bss
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window: .res 256 ; Memory "window"
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pagecount: .res 1 ; Number of available pages
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.code
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; ------------------------------------------------------------------------
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; INSTALL routine. Is called after the driver is loaded into memory. If
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; possible, check if the hardware is present and determine the amount of
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; memory available.
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; Must return an EM_ERR_xx code in a/x.
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;
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INSTALL:
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lda #$FF
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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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; 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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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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