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149 lines
4.0 KiB
ArmAsm
149 lines
4.0 KiB
ArmAsm
; Collection of functions that deal with tiles. Primarily rendering tile data into
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; the code fields.
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;
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; Tile data can be done faily often, so these routines are performance-sensitive.
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;
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; CopyTileConst -- the first 16 tile numbers are reserved and can be used
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; to draw a solid tile block
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; CopyTileLinear -- copies the tile data from the tile bank in linear order, e.g.
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; 32 consecutive bytes are copied
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; CopyTile
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;
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; A low-level function that copies 8x8 tiles directly into the code field space.
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;
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; A = Tile ID (0 - 1023)
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; X = Tile row (0 - 25)
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; Y = Tile columns (0 - 40)
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CopyTile
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phb ; save the current bank
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pha ; save the tile ID
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tya ; lookup the address of the virtual line (y * 8)
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asl
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asl
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asl
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asl
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tay
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sep #$20 ; set the bank register
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lda BTableHigh,y
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pha ; save for a few instruction
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rep #$20
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txa ; there are two columns per tile, so multiple by 4
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asl
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asl ; asl will clear the carry bit
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tax
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lda Col2CodeOffset,x
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adc BTableLow,y
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tay
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iny ; +1 to move past to opcode to the operand
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plb ; set the bank
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pla ; pop the tile ID
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jsr _CopyTile
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plb ; restore the data bank and return
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rts
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; _CopyTile
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;
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; Copy a solid tile into one of the code banks
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;
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; B = bank of the code field
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; A = Tile ID (0 - 1023)
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; Y = Base Adddress in the code field
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_CopyTile cmp #$0010
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bcc :FillWord
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cmp #$0400
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bcc :CopyTileMem
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rts ; Tile number is too large
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:TilePatterns dw $0000,$1111,$2222,$3333
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dw $4444,$5555,$6666,$7777
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dw $8888,$9999,$AAAA,$BBBB
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dw $CCCC,$DDDD,$EEEE,$FFFF
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:FillWord asl
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tax
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ldal :TilePatterns,x
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CopyTileConst sta: $0000,y
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sta: $0003,y
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sta $1000,y
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sta $1003,y
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sta $2000,y
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sta $2003,y
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sta $3000,y
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sta $3003,y
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sta $4000,y
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sta $4003,y
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sta $5000,y
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sta $5003,y
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sta $6000,y
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sta $6003,y
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sta $7000,y
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sta $7003,y
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rts
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:CopyTileMem 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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tax
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CopyTileLinear ldal tiledata+0,x
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sta: $0000,y
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ldal tiledata+2,x
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sta: $0003,y
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ldal tiledata+4,x
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sta $1000,y
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ldal tiledata+6,x
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sta $1003,y
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ldal tiledata+8,x
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sta $2000,y
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ldal tiledata+10,x
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sta $2003,y
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ldal tiledata+12,x
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sta $3000,y
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ldal tiledata+14,x
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sta $3003,y
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ldal tiledata+16,x
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sta $4000,y
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ldal tiledata+18,x
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sta $4003,y
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ldal tiledata+20,x
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sta $5000,y
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ldal tiledata+22,x
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sta $5003,y
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ldal tiledata+24,x
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sta $6000,y
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ldal tiledata+26,x
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sta $6003,y
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ldal tiledata+28,x
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sta $7000,y
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ldal tiledata+30,x
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sta $7003,y
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rts
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