111 lines
1.3 KiB
NASM
111 lines
1.3 KiB
NASM
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; ID_VL.ASM
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IDEAL
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MODEL MEDIUM,C
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INCLUDE 'ID_VL.EQU'
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SCREENSEG = 0a000h
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UPDATEWIDE = 20
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UPDATEHIGH = 13
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DATASEG
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EXTRN bufferofs :WORD
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EXTRN displayofs :WORD
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EXTRN ylookup :WORD
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EXTRN linewidth :WORD
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EXTRN blockstarts :WORD ;offsets from drawofs for each update block
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EXTRN update :BYTE
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CODESEG
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;=================
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;
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; VH_UpdateScreen
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;
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;=================
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PROC VH_UpdateScreen
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PUBLIC VH_UpdateScreen
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USES si,di
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mov dx,SC_INDEX
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mov ax,SC_MAPMASK+15*256
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out dx,ax
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mov dx,GC_INDEX
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mov al,GC_MODE
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out dx,al
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inc dx
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in al,dx
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and al,252
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or al,1
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out dx,al
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mov bx,UPDATEWIDE*UPDATEHIGH-1 ; bx is the tile number
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mov dx,[linewidth]
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;
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; see if the tile needs to be copied
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;
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@@checktile:
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test [update+bx],1
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jnz @@copytile
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@@next:
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dec bx
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jns @@checktile
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;
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; done
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;
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mov dx,GC_INDEX+1
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in al,dx
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and al,NOT 3
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or al,0
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out dx,al
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ret
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;
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; copy a tile
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;
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@@copytile:
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mov [update+bx],0
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shl bx,1
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mov si,[blockstarts+bx]
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shr bx,1
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mov di,si
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add si,[bufferofs]
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add di,[displayofs]
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mov ax,SCREENSEG
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mov ds,ax
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REPT 16
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mov al,[si]
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mov [di],al
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mov al,[si+1]
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mov [di+1],al
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mov al,[si+2]
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mov [di+2],al
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mov al,[si+3]
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mov [di+3],al
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add si,dx
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add di,dx
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ENDM
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mov ax,ss
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mov ds,ax
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jmp @@next
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ENDP
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END
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