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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').
276 lines
6.1 KiB
ArmAsm
276 lines
6.1 KiB
ArmAsm
;
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; Extended memory driver for the ISEPIC cartridge.
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; Marco van den Heuvel, 2010-01-24
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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_isepic_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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IP_WINDOW = $DF00 ; Address of ISEPIC window
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IP_CTRL_BASE = $DE00
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PAGES = 8
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; ------------------------------------------------------------------------
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; Code.
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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 #0
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sta IP_CTRL_BASE
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ldx IP_WINDOW
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cpx IP_WINDOW
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bne @notpresent
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inc IP_WINDOW
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cpx IP_WINDOW
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beq @notpresent
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ldx IP_WINDOW
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sta IP_CTRL_BASE+1
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inx
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stx IP_WINDOW
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dex
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sta IP_CTRL_BASE
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cpx IP_WINDOW
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beq @setok
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@notpresent:
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lda #<EM_ERR_NO_DEVICE
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ldx #>EM_ERR_NO_DEVICE
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rts
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@setok:
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lda #<EM_ERR_OK
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ldx #>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 #<PAGES
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ldx #>PAGES
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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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; The Isepic cartridge does not copy but actually map the window, so USE is
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; identical to MAP.
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USE := MAP
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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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tax
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sta IP_CTRL_BASE,x
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lda #<IP_WINDOW
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ldx #>IP_WINDOW
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; Use the RTS from COMMIT below to save a precious byte of storage
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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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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 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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; - tmp1 contains the low page register value
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; - X contains the page offset
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; - Y contains zero
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jmp @L5
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@L1:
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lda IP_WINDOW,x
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sta (ptr2),y
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iny
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bne @L2
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inc ptr2+1
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@L2:
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inx
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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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rts
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; Bump page register
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@L4:
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inc tmp1 ; Bump low page register
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@L5:
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stx tmp2
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ldx tmp1
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sta IP_CTRL_BASE,x
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ldx 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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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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; - tmp1 contains the low page register value
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; - X contains the page offset
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; - Y contains zero
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jmp @L5
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@L1:
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lda (ptr2),y
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sta IP_WINDOW,x
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iny
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bne @L2
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inc ptr2+1
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@L2:
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inx
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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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rts
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; Bump page register
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@L4:
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inc tmp1 ; Bump page register
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@L5:
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stx tmp2
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ldx tmp1
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sta IP_CTRL_BASE,x
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ldx 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 remember it.
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ldy #EM_COPY::PAGE
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lda (ptr1),y
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sta 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 X and clear Y
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ldy #EM_COPY::OFFS
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lda (ptr1),y
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tax
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ldy #0
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; Done
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rts
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