mirror of
https://github.com/cc65/cc65.git
synced 2024-12-27 15:29:46 +00:00
427 lines
9.6 KiB
ArmAsm
427 lines
9.6 KiB
ArmAsm
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;
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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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; ------------------------------------------------------------------------
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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 EMD_API_VERSION ; 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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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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