mirror of https://github.com/cc65/cc65.git
509 lines
12 KiB
ArmAsm
509 lines
12 KiB
ArmAsm
;
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; Extended memory driver for the C256K memory expansion
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; Marco van den Heuvel, 2010-01-27
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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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.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 _c64_c256k_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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BASE = $4000
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PAGES = 3 * 256
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TARGETLOC = $200 ; Target location for copy/check code
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PIA = $DFC0
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; ------------------------------------------------------------------------
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; Data.
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.data
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; This function is used to copy code from and to the extended memory
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.proc copy
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template:
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.org ::TARGETLOC ; Assemble for target location
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entry:
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stx PIA
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stashop = $91 ; 'sta' opcode
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operation := * ; Location and opcode is patched at runtime
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address := *+1
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lda ($00),y
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ldx #$dc
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stx PIA
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rts
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.reloc
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.endproc
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; This function is used to check for the existence of the extended memory
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.proc check
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template:
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.org ::TARGETLOC
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entry:
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ldy #$00 ; Assume hardware not present
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lda #$fc
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sta PIA
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lda $01
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tax
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and #$f8
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sta $01
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lda $4000
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cmp $c000
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bne done ; Jump if not found
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inc $c000
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cmp $4000
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beq done ; Jump if not found
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; Hardware is present
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iny
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done: stx $01
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ldx #$dc
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stx PIA
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rts
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.reloc
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.endproc
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.bss
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curpage: .res 2 ; Current page number
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curbank: .res 1 ; Current bank
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window: .res 256 ; Memory "window"
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; Since the functions above are copied to $200, the current contents of this
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; memory area must be saved into backup storage. Allocate enough space.
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backup: .res .max (.sizeof (copy), .sizeof (check))
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.code
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; ------------------------------------------------------------------------
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; INSTALL routine. Is called after the driver is loaded into memory. If
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; possible, check if the hardware is present and determine the amount of
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; memory available.
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; Must return an EM_ERR_xx code in a/x.
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;
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INSTALL:
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lda PIA+1 ; Select Peripheral Registers
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ora #4
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sta PIA+1
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tax
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lda PIA+3
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ora #4
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sta PIA+3
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tay
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lda #$DC ; Set the default memory bank data
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sta PIA
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lda #$FE
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sta PIA+2
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txa ; Select Data Direction Registers
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and #$FB
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sta PIA+1
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tya
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and #$FB
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sta PIA+3
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lda #$FF ; Set the ports to output
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sta PIA
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sta PIA+2
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txa
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and #$C7
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ora #$30 ; Set CA1 and
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sta PIA+1 ; select Peripheral Registers
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sty PIA+3
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jsr backup_and_setup_check_routine
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jsr check::entry
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cli
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ldx #.sizeof (check) - 1
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jsr restore_data
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cpy #$01
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beq @present
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lda #EM_ERR_NO_DEVICE
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ldx #0 ; return value is char
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rts
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@present:
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lda #EM_ERR_OK
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.assert EM_ERR_OK = 0, error
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tax
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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 #<PAGES
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ldx #>PAGES
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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:
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sei
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sta curpage ; Remember the new page
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stx curpage+1
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jsr adjust_page_and_bank
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stx curbank
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clc
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adc #>BASE
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sta ptr1+1
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ldy #0
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sty ptr1
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jsr backup_and_setup_copy_routine
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ldx #<ptr1
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stx copy::address
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@L1:
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ldx curbank
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jsr copy::entry
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ldx ptr1
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sta window,x
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inc ptr1
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bne @L1
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; Return the memory window
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jsr restore_copy_routine
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lda #<window
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ldx #>window ; Return the window address
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cli
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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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stx curpage+1
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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:
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sei
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lda curpage ; Get the current page
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ldx curpage+1
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jsr adjust_page_and_bank
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stx curbank
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clc
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adc #>BASE
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sta ptr1+1
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ldy #0
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sty ptr1
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jsr backup_and_setup_copy_routine
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ldx #<ptr1
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stx copy::address
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ldx #<copy::stashop
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stx copy::operation
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@L1:
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ldx ptr1
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lda window,x
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ldx curbank
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jsr copy::entry
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inc ptr1
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bne @L1
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; Return the memory window
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jsr restore_copy_routine
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done:
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cli
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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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sei
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jsr setup
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jsr backup_and_setup_copy_routine
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; Setup is:
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;
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; - ptr1 contains the struct pointer
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; - ptr2 contains the linear memory buffer
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; - ptr3 contains -(count-1)
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; - ptr4 contains the page memory buffer plus offset
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; - tmp1 contains zero (to be used for linear memory buffer offset)
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; - tmp2 contains the bank value
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lda #<ptr4
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sta copy::address
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jmp @L3
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@L1:
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ldx tmp2
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ldy #0
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jsr copy::entry
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ldy tmp1
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sta (ptr2),y
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inc tmp1
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bne @L2
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inc ptr2+1
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@L2:
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inc ptr4
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beq @L4
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; Bump count and repeat
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@L3:
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inc ptr3
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bne @L1
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inc ptr3+1
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bne @L1
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jsr restore_copy_routine
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cli
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rts
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; Bump page register
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@L4:
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inc ptr4+1
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lda ptr4+1
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cmp #$80
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bne @L3
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lda #>BASE
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sta ptr4+1
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lda tmp2
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clc
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adc #$10
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sta tmp2
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jmp @L3
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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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sei
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jsr setup
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jsr backup_and_setup_copy_routine
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; Setup is:
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;
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; - ptr1 contains the struct pointer
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; - ptr2 contains the linear memory buffer
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; - ptr3 contains -(count-1)
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; - ptr4 contains the page memory buffer plus offset
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; - tmp1 contains zero (to be used for linear memory buffer offset)
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; - tmp2 contains the bank value
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lda #<ptr4
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sta copy::address
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lda #<copy::stashop
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sta copy::operation
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jmp @L3
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@L1:
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ldy tmp1
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lda (ptr2),y
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ldx tmp2
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ldy #0
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jsr copy::entry
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inc tmp1
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bne @L2
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inc ptr2+1
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@L2:
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inc ptr4
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beq @L4
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; Bump count and repeat
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@L3:
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inc ptr3
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bne @L1
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inc ptr3+1
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bne @L1
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jsr restore_copy_routine
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cli
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rts
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; Bump page register
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@L4:
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inc ptr4+1
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lda ptr4+1
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cmp #$80
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bne @L3
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lda #>BASE
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sta ptr4+1
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lda tmp2
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clc
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adc #$10
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sta tmp2
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jmp @L3
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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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setup:
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sta ptr1
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stx ptr1+1 ; Save passed pointer
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; Get the page number from the struct and adjust it so that it may be used
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; with the hardware. That is: ptr4 has the page address and page offset
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; tmp2 will hold the bank value
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ldy #EM_COPY::PAGE+1
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lda (ptr1),y
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tax
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ldy #EM_COPY::PAGE
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lda (ptr1),y
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jsr adjust_page_and_bank
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clc
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adc #>BASE
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sta ptr4+1
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stx tmp2
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; Get the buffer pointer into ptr2
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ldy #EM_COPY::BUF
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lda (ptr1),y
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sta ptr2
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iny
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lda (ptr1),y
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sta ptr2+1
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; Get the count, calculate -(count-1) and store it into ptr3
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ldy #EM_COPY::COUNT
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lda (ptr1),y
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eor #$FF
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sta ptr3
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iny
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lda (ptr1),y
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eor #$FF
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sta ptr3+1
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; Get the page offset into ptr4 and clear tmp1
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ldy #EM_COPY::OFFS
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lda (ptr1),y
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sta ptr4
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lda #0
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sta tmp1
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; Done
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rts
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; Helper routines for copying to and from the +256k ram
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backup_and_setup_copy_routine:
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ldx #.sizeof (copy) - 1
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@L1:
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lda copy::entry,x
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sta backup,x
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lda copy::template,x
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sta copy::entry,x
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dex
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bpl @L1
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rts
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backup_and_setup_check_routine:
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ldx #.sizeof (check) - 1
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@L1:
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lda check::entry,x
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sta backup,x
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lda check::template,x
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sta check::entry,x
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dex
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bpl @L1
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rts
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restore_copy_routine:
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ldx #.sizeof (copy) - 1
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restore_data:
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lda backup,x
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sta TARGETLOC,x
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dex
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bpl restore_data
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rts
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; Helper routine to correct for the bank and page
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adjust_page_and_bank:
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sta tmp4
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lda #$0C
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sta tmp3
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lda tmp4
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and #$c0
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lsr
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lsr
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ora tmp3
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sta tmp3
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txa
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asl
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asl
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asl
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asl
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asl
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asl
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ora tmp3
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tax
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lda tmp4
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and #$3f
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rts
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