184 lines
7.1 KiB
ArmAsm
184 lines
7.1 KiB
ArmAsm
; Initialize the system for fun!
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;
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; Mostly memory allocation
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;
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; * 13 banks of memory for the blitter
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; * 1 bank of memory for the second background
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; * 1 bank of memory for the second background alt/mask
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;
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; * $01/2000 - $01/9FFF for the shadow screen
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; * $00/2000 - $00/9FFF for the fixed background
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;
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; * 10 pages of direct page in Bank $00
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; - 1 page for scratch space
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; - 1 page for pointer to the second background
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; - 8 pages for the dynamic tiles
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mx %00
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InitMemory lda EngineMode
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bit #ENGINE_MODE_BNK0_BUFF
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beq :no_bnk0_buff
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PushLong #0 ; space for result
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PushLong #$008000 ; size (32k)
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PushWord UserId
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PushWord #%11000000_00010111 ; Fixed location
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PushLong #$002000
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_NewHandle ; returns LONG Handle on stack
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plx ; base address of the new handle
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pla ; high address 00XX of the new handle (bank)
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:no_bnk0_buff
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PushLong #0 ; space for result
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PushLong #$008000 ; size (32k)
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PushWord UserId
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PushWord #%11000000_00010111 ; Fixed location
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PushLong #$012000
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_NewHandle ; returns LONG Handle on stack
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plx ; base address of the new handle
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pla ; high address 00XX of the new handle (bank)
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PushLong #0 ; space for result
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pea #0000 ; size (2 or 10 pages)
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lda EngineMode
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bit #ENGINE_MODE_DYN_TILES
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beq :no_dyn_tiles
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pea #$0A00 ; 10 pages if dynamic tiles are enabled
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bra :dyn_done
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:no_dyn_tiles pea #$0200 ; 2 pages if dynamic tiles are disabled
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:dyn_done
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PushWord UserId
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PushWord #%11000000_00010101 ; Page-aligned, fixed bank
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PushLong #$000000
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_NewHandle ; returns LONG Handle on stack
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plx ; base address of the new handle
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pla ; high address 00XX of the new handle (bank)
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_Deref
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stx BlitterDP
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; Allocate banks of memory for BG1. If the user wants to swap between multiple BG1 banks, then they need to be allocated
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; outside of GTE and selected using the GTESetBG1Bank() function. Passing a zero for that function's argument will
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; always set the bank to the allocated bank number. Bank 00 and Bank 01 are illegal values.
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lda EngineMode
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bit #ENGINE_MODE_TWO_LAYER
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beq :no_bg1
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jsr AllocOneBank2
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sta BG1DataBank
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:no_bg1
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jsr AllocOneBank2
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sta CompileBank
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stz CompileBank0
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; Allocate the 13 banks of memory we need and store in double-length array
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]step equ 0
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lup 13
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jsr AllocOneBank2
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sta BlitBuff+]step+2
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stz BlitBuff+]step
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]step equ ]step+4
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--^
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; Fill in a table with the adddress of all 208 scanlines across all 13 banks. Also fill in
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; a shorter table that just holds the starting address of the 26 tile block rows.
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ldx #0
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ldy #0
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:bloop
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lda BlitBuff+2,y ; Copy the high word first
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]step equ 0
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lup 16
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sta BTableHigh+]step,x ; 16 lines per bank
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sta BTableHigh+]step+{208*2},x ; 16 lines per bank
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]step equ ]step+2
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--^
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lda BlitBuff,y
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sta BTableLow,x
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sta BTableLow+{208*2},x
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clc
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]step equ 2
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lup 15
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adc #$1000
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sta BTableLow+]step,x
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sta BTableLow+]step+{208*2},x
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]step equ ]step+2
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--^
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txa
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clc
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adc #16*2 ; move to the next chunk of BTableHigh and BTableLow
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tax
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tya
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clc
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adc #4 ; move to the next bank address
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tay
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cmp #4*13
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bcs :exit1
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brl :bloop
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:exit1
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ldx #0
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ldy #0
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:bloop2
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lda BlitBuff+2,y ; Copy the high word first
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sta BRowTableHigh,x ; Two rows per bank
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sta BRowTableHigh+{26*2},x
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sta BRowTableHigh+2,x
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sta BRowTableHigh+{26*2}+2,x
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lda BlitBuff,y
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sta BRowTableLow,x
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sta BRowTableLow+{26*2},x
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clc
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adc #$8000
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sta BRowTableLow+2,x
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sta BRowTableLow+{26*2}+2,x
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txa
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adc #4
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tax
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tya
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adc #4 ; move to the next bank address
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tay
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cmp #4*13
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bcs :exit
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brl :bloop2
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:exit
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rts
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; Bank allocator (for one full, fixed bank of memory. Can be immediately deferenced)
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AllocOneBank PushLong #0
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PushLong #$10000
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PushWord UserId
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PushWord #%11000000_00011100
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PushLong #0
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_NewHandle ; returns LONG Handle on stack
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plx ; base address of the new handle
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pla ; high address 00XX of the new handle (bank)
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xba ; swap accumulator bytes to XX00
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stal :bank+2 ; store as bank for next op (overwrite $XX00)
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:bank ldal $000001,X ; recover the bank address in A=XX/00
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rts
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; Variation that returns the pointer in the X/A registers (X = low, A = high)
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AllocOneBank2 PushLong #0
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PushLong #$10000
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PushWord UserId
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PushWord #%11000000_00011100
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PushLong #0
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_NewHandle
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plx ; base address of the new handle
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pla ; high address 00XX of the new handle (bank)
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_Deref
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rts
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