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80 lines
2.0 KiB
ArmAsm
80 lines
2.0 KiB
ArmAsm
* AUXMEM.GFX.S
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* (c) Bobbi 2021 GPLv3
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*
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* Graphics operations
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* Convert high-resolution screen coordinates
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* from 1280x1024 to 280x192
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CVTCOORD
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* X-coordinate in VDUQ+5,+6 1280*7/32=280
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LDA VDUQ+6 ; X-coord -> ZP1 and ZP2
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STA ZP1+1
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STA ZP2+1
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LDA VDUQ+5
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STA ZP1+0
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ASL A ; ZP2 *= 8
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ROL ZP2+1
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ASL A
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ROL ZP2+1
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ASL A
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ROL ZP2+1
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SEC ; ZP2-ZP1->ZP2
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SBC ZP1+0
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STA ZP2+0
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LDA ZP2+1
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SBC ZP1+1
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LSR A ; ZP2 /= 32
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ROR ZP2+0
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LSR A
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ROR ZP2+0
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LSR A
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ROR ZP2+0
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LSR A
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ROR ZP2+0
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LSR A
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ROR ZP2+0
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STA VDUQ+6 ; ZP2 -> X-coord
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LDA ZP2+0
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STA VDUQ+5
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* Y-coordinate in VDUQ+7,+8 1024*3/16=192
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LDA VDUQ+8 ; Y-coord -> ZP1
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STA ZP1+1
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STA ZP2+1
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LDA VDUQ+7
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STA ZP1+0
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ASL A ; ZP2 *= 2
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ROL ZP2+1
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CLC ; ZP2+ZP1->ZP2
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ADC ZP1+0
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STA ZP2+0
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LDA ZP2+1
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ADC ZP1+1
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LSR A ; ZP2 /= 16
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ROR ZP2+0
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LSR A
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ROR ZP2+0
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LSR A
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ROR ZP2+0
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LSR A
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STA VDUQ+8 ; ZP2 -> Y-coord
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LDA ZP2+0
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ROR
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STA VDUQ+7
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RTS
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* Add coordinates to XPIXEL, YPIXEL
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RELCOORD CLC
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LDA XPIXEL+0
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ADC VDUQ+5
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STA VDUQ+5
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LDA XPIXEL+1
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ADC VDUQ+6
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STA VDUQ+6
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CLC
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LDA YPIXEL
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ADC VDUQ+7
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STA VDUQ+7
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RTS
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