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detect number of RAM pages
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mrdudz
parent
8db0def88b
commit
8e19d84cb4
@ -1,15 +1,9 @@
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;
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;Extended Memory Driver for the Retro Replay RAM (32k)
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;should work for ActionReplay as well...
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;
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; Extended Memory Driver for the Action Replay/Retro Replay RAM
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;
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; original Version 1.0 by Johannes Braun 2006-08-22 <hannenz@freenet.de>
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;
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;use the functions described in "usr/lib/cc65/include/em.h" to make use of this driver.
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; ------------------------------------------------------------------------
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;NOTE: If called from ROM the Lo_Code routines must exit with LDA #$00 / STA $DE00!!! just change and recompile!
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.include "zeropage.inc"
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.include "em-kernel.inc"
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@ -28,6 +22,9 @@ temp = tmp1
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Lo_Mem = $0100 ; location of Lo_Code (must be below $1000 or above $e000)
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RRMODE_OFF = $02
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RRMODE_CART_RAM = $23
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; ------------------------------------------------------------------------
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; Header. Includes jump table
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@ -54,9 +51,11 @@ Lo_Mem = $0100 ; location of Lo_Code (must be below $1000 or above $e000)
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.addr COPYTO
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; ------------------------------------------------------------------------
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; Data.
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.bss
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window: .res 256 ; the memory window (256 bytes)
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window: .res 256 ; the memory window (256 bytes)
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pagecount: .res 1 ; Number of available pages
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.rodata
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dummy:
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@ -79,62 +78,118 @@ INSTALL:
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sta Lo_Mem,x
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dex
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bpl :-
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stx curpage ; invalidate current page ($ff)
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;ldx #$ff
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stx curpage ; invalidate current page
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ldx #$23 ; $de00 value for rr-ram
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ldy #$02 ; $de00 value for c64-ram, CHANGE TO LDA #$00 if driver is called from ROM!
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bne COMMON
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ldy #RRMODE_OFF
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sei
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jmp Lo_Mem+8 ; jump to the code below
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c1: stx $de00 ; try accessing rr-ram
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; copied to Lo_Mem
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c1:
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;detectmodes:
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.byte RRMODE_CART_RAM | $00
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.byte RRMODE_CART_RAM | $08
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.byte RRMODE_CART_RAM | $10
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.byte RRMODE_CART_RAM | $18
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.byte RRMODE_CART_RAM | $80
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.byte RRMODE_CART_RAM | $88
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.byte RRMODE_CART_RAM | $90
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.byte RRMODE_CART_RAM | $98
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; first save c64 memory
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lda $8888
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pha
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lda $9999 ; remember old content of $8888 and $9999
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pha
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lda #$55
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sta $8888 ; write test values
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; tag c64 memory
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lda #$00
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sta $8888
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ldx #$07
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:
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; try accessing rr-ram
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;lda detectmodes, x
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lda Lo_Mem, x
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sta $de00
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; tag (hopefully) rr memory
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txa
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ora #$80
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sta $8888
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dex
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bpl :-
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;ldy #RRMODE_OFF
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sty $de00
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; now if C64 memory is $80, there is no AR/RR
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; if C64 memory is $00, there is a AR/RR.
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lda $8888
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beq detectpages
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lda #0
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beq hasnopages
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detectpages:
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; we can now read the highest available bank nr from the highest bank :)
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lda #RRMODE_CART_RAM | $98
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sta $de00
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ldx $8888
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inx
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txa
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; 8k = 32 pages
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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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sta $9999
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sty $de00 ; switch to c64 ram
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stx $8888
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stx $9999
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hasnopages:
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stx $de00 ; switch to rr-ram again (if present)
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ldx $8888 ; read the values
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ldy $9999
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pla
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sta $9999 ; and write the old values back
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;ldy #RRMODE_OFF
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sty $de00 ; c64 ram again
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sta pagecount
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; restore c64 memory
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pla
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sta $8888
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lda #2
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sta $de00 ; c64 ram again
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cli
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cpx #$55
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bne no
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cpy #$aa
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bne no
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ldx pagecount
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beq no
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; no error
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lda #0
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tax
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rts
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no: asl ; A still has #2, so return #4: error code for "device not present"
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no:
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lda #4 ; return #4: error code for "device not present"
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rts
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c2:
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;----------------------------------------------------------------------------------------
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;void em_uninstall(void);
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;----------------------------------------------------------------------------------------
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UNINSTALL:
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return_null:
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lda #$00 ; always return 32kb (128 pages)
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; fall through, skip the LDA
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.byte $2c
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lda #$00
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tax
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rts
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;----------------------------------------------------------------------------------------
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;unsigned __fastcall__ em_pagecount(void);
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;----------------------------------------------------------------------------------------
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PAGECOUNT:
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lda #$80
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lda pagecount ; always return 32kb (128 pages)
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ldx #$00
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rts
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@ -154,7 +209,7 @@ return: rts
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;void* __fastcall__ em_map(unsigned page);
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;----------------------------------------------------------------------------------------
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MAP:
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cmp #$80
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cmp pagecount
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bcs return_null
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sta curpage
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lda #<dummy ; load .A/.X with adress of data for COPYFROM-call (which expects the
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@ -167,7 +222,7 @@ MAP:
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;----------------------------------------------------------------------------------------
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COMMIT:
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lda curpage
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cmp #$80
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cmp pagecount
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bcs return
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lda #<dummy ; load .A/.X with adress of data for COPYTO-call (which expects the
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ldx #>dummy ; adress in .A/.X)
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@ -192,6 +247,7 @@ COMMON:
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;this part will be executed in Lo_Mem (!) by COPYFROM
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Lo_Code2:
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; copy byte rr -> c64
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stx $de00 ;map in rr-ram
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lda (rr_ram),y ;get byte from rr-ram
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sty $de00 ;RR-ROM will be mapped to $8000-$a000 but write access will go to c64-ram anyway!!
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@ -204,6 +260,7 @@ Lo_Code2_End:
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;this part will be executed in Lo_Mem (!) by COPYTO
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Lo_Code1:
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; copy byte c64 -> rr
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lda (c64_ram),y ;read 1 byte from c64-ram
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stx $de00 ;map in rr-ram
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sta (rr_ram),y ;write byte to rr-ram
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