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https://github.com/cc65/cc65.git
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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').
431 lines
9.8 KiB
ArmAsm
431 lines
9.8 KiB
ArmAsm
;
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; Extended memory driver for the C128 RAM in banks #1, #2 and #3. Driver works without
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; problems when statically linked.
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;
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; Ullrich von Bassewitz, 2002-12-04
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;
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; Updated to use banks 2 and 3 as well by
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; Marco van den Heuvel, 2010-01-21
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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 "c128.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 _c128_ram2_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 = $400
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; ------------------------------------------------------------------------
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; Data.
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.bss
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curpage: .res 2 ; Current page number
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curbank: .res 1 ; Current bank number
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copybank: .res 2 ; temp bank number
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window: .res 256 ; Memory "window"
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pagecount: .res 2 ; 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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ldx #0
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stx ptr1
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ldx #4
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stx ptr1+1
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ldx #<ptr1
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stx FETVEC
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stx STAVEC
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ldy #0
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ldx #MMU_CFG_RAM1
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jsr FETCH
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sta tmp1
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ldx #MMU_CFG_RAM3
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jsr FETCH
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cmp tmp1
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bne @has_4_banks
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tax
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inx
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txa
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ldx #MMU_CFG_RAM1
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jsr STASH
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ldx #MMU_CFG_RAM3
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jsr FETCH
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cmp tmp1
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beq @has_4_banks
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ldx #0
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lda #251
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bne @setok
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@has_4_banks:
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ldx #2
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lda #241
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@setok:
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sta pagecount
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stx pagecount+1
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ldx #$FF
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stx curpage
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stx curpage+1 ; Invalidate the current page
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inx
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txa ; A = X = 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 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: sei
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sta curpage
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stx curpage+1 ; Remember the new page
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jsr calculate_bank_and_correct_page
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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 #$00
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sty ptr1
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lda #<ptr1
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sta FETVEC
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; Transfer one page
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@L1: ldx curbank
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jsr getcurbankmmu
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jsr FETCH
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sta window,y
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iny
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bne @L1
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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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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
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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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rts
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; ------------------------------------------------------------------------
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; COMMIT: Commit changes in the memory window to extended storage.
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COMMIT: sei
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lda curpage ; Get the current page
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ldx curpage+1
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bmi done ; Jump if no page mapped
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jsr calculate_bank_and_correct_page
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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 #$00
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sty ptr1
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lda #<ptr1
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sta STAVEC
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; Transfer one page. Y must be zero on entry
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@L1: lda window,y
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ldx curbank
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jsr getcurbankmmu
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jsr STASH
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iny
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bne @L1
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cli
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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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sei
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jsr setup
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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 buffer and offset
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; - tmp1 contains the bank
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; - tmp2 contains zero (used for linear memory buffer offset)
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lda #<ptr4
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sta FETVEC
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jmp @L3
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@L1: ldx tmp1
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jsr getcurbankmmu
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ldy #0
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jsr FETCH
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ldy tmp2
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sta (ptr2),y
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inc tmp2
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bne @L2
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inc ptr2+1
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@L2: inc ptr4
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beq @L4
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; Bump count and repeat
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@L3: 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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cli
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rts
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; Bump page register
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@L4: inc ptr4+1
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lda ptr4+1
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cmp #$ff
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bne @L3
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lda #4
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sta ptr4+1
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inc tmp1
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@L5:
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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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; 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 buffer and offset
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; - tmp1 contains the bank
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; - tmp2 contains zero (used for linear memory buffer offset)
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lda #<ptr4
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sta STAVEC
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jmp @L3
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@L1:
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ldy tmp2
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lda (ptr2),y
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ldx tmp1
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jsr getcurbankmmu
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ldy #0
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jsr STASH
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inc tmp2
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bne @L2
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inc ptr2+1
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@L2: inc ptr4
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beq @L4
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; Bump count and repeat
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@L3: 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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cli
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rts
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; Bump page register
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@L4: inc ptr4+1
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lda ptr4+1
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cmp #$ff
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bne @L3
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inc tmp1
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lda #4
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sta ptr4+1
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@L5:
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jmp @L3
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; ------------------------------------------------------------------------
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; Helper function to calculate the correct bank and page
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; when addressing bank 2 or 3
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calculate_bank_and_correct_page:
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cpx #2
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beq @calculate_bank_3_with_2
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cpx #1
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beq @calculate_bank_2_or_3_with_1
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sec
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sbc #251
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bcs @calculate_bank_2_with_0
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ldx #1
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lda curpage
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rts
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@calculate_bank_3_with_2:
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lda curpage
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clc
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adc #10
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@calculate_bank_3_with_1:
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ldx #3
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rts
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@calculate_bank_2_or_3_with_1:
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sec
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sbc #246
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bcs @calculate_bank_3_with_1
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lda curpage
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clc
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adc #5
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@calculate_bank_2_with_0:
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ldx #2
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rts
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; ------------------------------------------------------------------------
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; Helper function to get the correct mmu value in x
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getcurbankmmu:
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cpx #1
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beq @bank1
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cpx #2
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beq @bank2
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ldx #MMU_CFG_RAM3
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rts
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@bank2:
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ldx #MMU_CFG_RAM2
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rts
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@bank1:
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ldx #MMU_CFG_RAM1
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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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setup: 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: page pointer in ptr4 and bank in tmp1
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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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dey
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lda (ptr1),y
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sta curpage
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jsr calculate_bank_and_correct_page
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clc
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adc #4
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sta ptr4+1
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stx tmp1
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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 the low byte of ptr4 clear tmp2
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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 tmp2
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; Done
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rts
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