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237 lines
6.7 KiB
ArmAsm
237 lines
6.7 KiB
ArmAsm
;
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; Extended memory driver for the Commodore REU. Driver works without
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; problems when statically linked.
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;
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; Ullrich von Bassewitz, 2002-11-29
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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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; ------------------------------------------------------------------------
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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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REU_STATUS = $DF00 ; Status register
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REU_COMMAND = $DF01 ; Command register
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REU_C64ADDR = $DF02 ; C64 base address register
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REU_REUADDR = $DF04 ; REU base address register
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REU_COUNT = $DF07 ; Transfer count register
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REU_IRQMASK = $DF09 ; IRQ mask register
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REU_CONTROL = $DF0A ; Control register
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REU_TRIGGER = $FF00 ; REU command trigger
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OP_COPYFROM = $ED
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OP_COPYTO = $EC
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; ------------------------------------------------------------------------
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; Data.
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.bss
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pagecount: .res 2 ; Number of pages available
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curpage: .res 2 ; Current page number
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window: .res 256 ; Memory "window"
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reu_params: .word $0000 ; Host address, lo, hi
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.word $0000 ; Exp address, lo, hi
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.byte $00 ; Expansion bank no.
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.word $0000 ; # bytes to move, lo, hi
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.byte $00 ; Interrupt mask reg.
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.byte $00 ; Adress control reg.
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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 #$00 ; High byte of return code
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lda #$55
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sta REU_REUADDR
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cmp REU_REUADDR ; Check for presence of REU
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bne nodevice
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asl a ; A = $AA
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sta REU_REUADDR
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cmp REU_REUADDR ; Check for presence of REU
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bne nodevice
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ldy #>(128*4) ; Assume 128KB
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lda REU_STATUS
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and #$10 ; Check size bit
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beq @L1
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ldy #>(256*4) ; 256KB when size bit is set
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@L1: sty pagecount+1
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ldy #$FF
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sty curpage
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sty curpage+1 ; Invalidate the current page
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txa ; X = A = EM_ERR_OK
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rts
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; No REU found
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nodevice:
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lda #EM_ERR_NO_DEVICE
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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: sta curpage
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stx curpage+1 ; Remember the new page
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ldy #OP_COPYFROM
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jsr common ; Copy the window
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lda #<window
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ldx #>window ; Return the window address
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done: 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: lda curpage
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ldx curpage+1 ; Do we have a page mapped?
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bmi done ; Jump if no page mapped
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ldy #OP_COPYTO
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common: sty tmp1
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ldy #<window
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sty REU_C64ADDR
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ldy #>window
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sty REU_C64ADDR+1
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ldy #0
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sty REU_REUADDR+0
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sta REU_REUADDR+1
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stx REU_REUADDR+2
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sty REU_COUNT+0
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ldy #1
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sty REU_COUNT+1 ; Move 256 bytes
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bne transfer1 ; Transfer 256 bytes into REU
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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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ldy #OP_COPYFROM
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.byte $2C
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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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ldy #OP_COPYTO
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sty tmp1
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; Remember the passed pointer
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sta ptr1
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stx ptr1+1 ; Save the pointer
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; The structure passed to the functions has the same layout as the registers
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; of the Commodore REU, so register programming is easy.
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ldy #7-1
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@L1: lda (ptr1),y
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sta REU_C64ADDR,y
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dey
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bpl @L1
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; Invalidate the page in the memory window
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sty curpage+1 ; Y = $FF
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; Reload the REU command and start the transfer
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transfer1:
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ldy tmp1
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; Transfer subroutine for the REU. Expects command in Y.
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transfer:
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sty REU_COMMAND ; Issue command
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ldy $01 ; Save the value of the c64 control port...
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tya ;
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and #$F8 ; Disable ROMs and I/O.
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sei ;
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sta $01
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lda REU_TRIGGER ; Don't change $FF00
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sta REU_TRIGGER ; Start the transfer...
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sty $01 ; Restore the old configuration
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cli
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rts
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