mirror of
https://github.com/RevCurtisP/C02.git
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100 lines
3.3 KiB
Plaintext
100 lines
3.3 KiB
Plaintext
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; Vera Display Composer Assembly Language Routines for C02
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; Requires External Routines NYBCAT, NYBCUT, REGADR, and SAVRXY
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; and External Variables TEMP1 and TEMP2
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;rgbclr(r,g,b) - Convert RGB Values to Palette Color
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;Args: A = Red Value (0-15)
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; Y = Green Value (0-15)
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; X = Blue Value (0-15)
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;Affects: A
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;Returns: Y = Color MSB (0000RRRR)
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; X = Color LSB (GGGGBBBB)
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RGBCLR: PHA ;Save Red Value
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TYA ;Copy Green Value to Left Nybble
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.DC $DA ;PHX Copy Blue Value
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.DC $7A ;PLY to Right Nybble
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JSR NYBCAT ;Concatanate Green and Blue
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TAX ;and Return as LSB
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.DC $7A ;PLY Return Red as MSB
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RTS
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;clrrgb(c) - Convert Palette Color to RGB Values
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;Args: Y = Color MSB (0000RRRR)
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; X = Color LSB (GGGGBBBB)
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;Returns: A = Red Value (0-15)
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; Y = Green Value (0-15)
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; X = Blue Value (0-15)
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CLRRGB: .DC $5A ;PHY Save MSB
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TXA ;Copy LSB into Accumulator
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JSR NYBCUT ;and Split into Nybbles
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.DC $5A ;PHY Return Blue Value
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.DC $FA ;PLX in X Register
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TAY ;Green Value in Y Register
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PLA ;and Red Value in Accumulator
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RTS
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;getclr(idx) - Get Color Entry idx from Paleftte
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;Args: A = Color Entry Index
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;Affects: A
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;Returns: Y = Color MSB (0000RRRR)
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; X = Color LSB (GGGGBBBB)
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GETCLR: JSR SETIDX ;Set Vera Address to Palette Index
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LDX $9F25 ;Get Current Data Port
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LDA $9F23,X ;Read LSB from Data Port
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LDY $9F23,X ;Read MSB from Data Port
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TAX ;Copy LSB to X Register
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RTS
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;setclr(idx) - Set Color Entry idx in Palette
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;Args: A = Color Entry Index
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; Y = Color MSB (0000RRRR)
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; X = Color LSB (GGGGBBBB)
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;Affects: A
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;Returns: Y,X = Color Entry Address
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SETCLR: JSR SAVRXY ;Save Color Value
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JSR SETIDX ;Set Vera Address to Palette Index
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LDX $9F25 ;Get Current Data Port
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LDA TEMP1 ;Retrieve Color Value LSB
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STA $9F23,X ;and Write to Data Port
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LDA TEMP2 ;Retrieve Color Value MSB
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STA $9F23,X ;Read MSB from Data Port
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RTS
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;setidy(idx) - Set Palette Index and Entry Count
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;Args: A = Palette Index
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; Y = Number of Entries
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;Returns: A = Bank + Auto-Increment
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; Y,X = Address
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SETIDY: STY TEMP0 ;Store Number of Colors
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ASL TEMP0 ;and Multiply by 2
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;setidx(idx) - Set Vera Address to Palette Index
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;Args: A = Index
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;Returns: A = Bank + Auto-Increment
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; Y,X = Address
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SETIDX: ASL ;Multiply Index by 2
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TAX ;and Set as LSB
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LDA #$10 ;Get Palette Page
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ADC #$00 ;Add Carry from Multiply
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TAY ;and Set as MSB
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JMP REGADR ;and Set Address to Register
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;getplt(idx,num) - Set Palette Colors
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;Args: A = Starting Index
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; Y = Number of Colors (1-128)
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;Uses: DSTLO,DSTHI = Address of Destination Array
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;Affects: A,X,Y
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GETPLT: JSR SETIDY ;Set Vera Address and Entry Count
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JMP GETMEA ;Read Color Entries from Vera Memory
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;setplt(idx,num) - Set Palette Colors
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;Args: A = Starting Index
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; Y = Number of Colors (1-128)
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;Uses: SRCLO,SRCHI = Address of Color Entries
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;Affects: A,X,Y
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SETPLT: JSR SETIDY ;Set Vera Address and Entry Count
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JMP SETMEA ;Write Color Entries to Vera Memory
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