; ============================================================================== ; ; 3D Copper Demo ; D. Munsie 2003, 2011 ; ; Based on the 3D Copper demo for the GBA ; ; ============================================================================== ; ------------------------------------------------------------------------------ ; ; Revision History: ; Oct 2011 Many changes to reduce ROM size and RAM usage, added 2 additional ; copper bars. Reset switch now pauses animation, Color/B&W switch ; switches between 4 and 6 copper bar mode. ; 06 Jul 03 Implemented changes suggested by DEBRO to get 262 scan lines and ; insure 2600jr compatibility ; 02 Jul 03 Initial release ; ; ------------------------------------------------------------------------------ processor 6502 include vcs.h ; ------------------------------------------------------------------------------ ; Consts ; ------------------------------------------------------------------------------ seg.u Consts TopBlankLines = 50 ; number of blank lines on the top NumTopLines = 25 ; number of lines in the copper bar area above the text NumMiddleLines = 40 ; number of lines in the copper bar area with text NumBottomLines = 26 ; number of lines in the copper bar area below the text BottomBlankLines = 51 ; number of blank lines on the bottom NumColorLines = NumTopLines + NumMiddleLines + NumBottomLines ; ------------------------------------------------------------------------------ ; Zero Page Variables ; ------------------------------------------------------------------------------ seg.u ZeroPage org $80 LineColor ds NumColorLines ; wow -- i'm pretty insane... i'm using over half of ; my RAM for a color table... oh well, it is just a ; demo :) NumBars ds 1 ; number of bars we are displaying BarPositions ds 6 ; Middle lines of the bar BarDepths ds 6 ; Depths of the bars BarAngles ds 6 ; Angles of the bars BarColors ds 6 ; Colors of the bars TmpVar ds 1 ; temporary variable ; make sure we didn't go over our RAM allotment if . > $100 echo "ERR", . - $80, "bytes of RAM used, but only $80 available." err endif ; ------------------------------------------------------------------------------ ; Start of ROM ; ------------------------------------------------------------------------------ seg Code org $f800 ROMStart ; ------------------------------------------------------------------------------ ; Playfield tables -- located at start of the ROM to minimize ROM space waste ; due to alignment requirements ; ------------------------------------------------------------------------------ PF0FirstTable byte %00100000 byte %00100000 byte %11100000 byte %00100000 byte %11000000 PF1FirstTable byte %10101001 byte %10101001 byte %10101111 byte %10101001 byte %01110110 PF2FirstTable byte %01010010 byte %01010010 byte %01001110 byte %01010010 byte %01001110 PF0SecondTable byte %11000000 byte %10000000 byte %00000000 byte %01000000 byte %10000000 PF1SecondTable byte %11001100 byte %00010010 byte %10011110 byte %01010000 byte %10001100 PF2SecondTable byte %00100010 byte %01010101 byte %01010101 byte %01010101 byte %00100010 ; ------------------------------------------------------------------------------ ; Variable initialization ; ------------------------------------------------------------------------------ VarInit4Bars subroutine lda #$04 ; save off the number of bars we are currently displaying sta NumBars tay .loop dey lda Bar4StartAngleValues,y sta BarAngles,y lda BarStartColorValues,y sta BarColors,y cpy #0 bne .loop ; done? rts VarInit6Bars subroutine lda #$06 ; save off the number of bars we are currently displaying sta NumBars tay .loop dey lda Bar6StartAngleValues,y sta BarAngles,y lda BarStartColorValues,y sta BarColors,y cpy #0 bne .loop ; done? rts ; ------------------------------------------------------------------------------ ; Main entry point ; ------------------------------------------------------------------------------ Main subroutine sei ; disable interrupts cld ; turn off decimal mode ldx #$ff ; setup the stack pointer txs lda #0 ; clear out zero page .zeroPageLoop pha ; by using the stack pointer dex bne .zeroPageLoop pha ; get mem $00 as well, and reset the SP back to $ff ; ------------------------------------------------------------------------------ ; Main Loop ; ------------------------------------------------------------------------------ MainLoop lda #$08 ; check the status of the B/W & Color switch bit SWCHB bne .colorSet ; color is selected == 6 bars lda NumBars ; see if we currently have 4 bars selected cmp #$04 beq .checkReset ; yes -- move on, nothing to do here jsr VarInit4Bars jmp UpdateBars ; skip the reset check this frame .colorSet lda NumBars ; see if we currently have 6 bars selected cmp #$06 beq .checkReset ; yes -- move on, nothing to do here jsr VarInit6Bars jmp UpdateBars ; skip the reset check this frame .checkReset lda #$01 ; check if someone is holding down reset bit SWCHB beq EraseBars ; yes -- skip the updates ; ------------------------------------------------------------------------------ ; Update bar positions ; ------------------------------------------------------------------------------ UpdateBars subroutine ldy NumBars .loop dey ; move to the next bar ldx BarAngles,y ; get the bar angle dex ; move it stx BarAngles,y ; store it for next time lda PositionTable,x ; get the postion sta BarPositions,y txa ; DepthTable is packed. Each entry represents 8 angles lsr ; so divide by 8 lsr lsr cmp #$10 ; check if we are indexing into the non-existant half bcc .skipInvert ; nope sta TmpVar ; we are -- save off the current index lda #$10 ; we need to subtract it off from $10 clc ; we DO NOT want to use the carry bit sbc TmpVar ; subtract the index from $10 and #$0f ; and make sure it's < $10 now .skipInvert tax lda DepthTable,x ; get the depth value sta BarDepths,y cpy #0 bne .loop ; done? ; ------------------------------------------------------------------------------ ; Sort bar depths ; ; This routine sorts the depths so that when the bars are "drawn", the ones ; with a smaller depth are drawn first. It does this by comparing depth 4 to ; depths 1-3, followed by depth 3 to depths 1-2, and depth2 to depth 1. After ; doing this, the bars will be sorted. ; ------------------------------------------------------------------------------ SortBars subroutine ldx NumBars ; start comparing .outerLoop dex ; move to the next depth to check beq .exit ; is this the end? txa ; move over the current depth for the inner loop tay .innerLoop dey ; check the next depth lda BarDepths,x ; is this depth cmp BarDepths,y ; more than this one? bcs .noSwap ; if so, we don't need to swap pha ; swap the depths - we already have BarDepths,x lda BarDepths,y sta BarDepths,x pla sta BarDepths,y lda BarColors,x ; swap the colors pha lda BarColors,y sta BarColors,x pla sta BarColors,y lda BarPositions,x ; swap the position pha lda BarPositions,y sta BarPositions,x pla sta BarPositions,y lda BarAngles,x ; swap the angle pha lda BarAngles,y sta BarAngles,x pla sta BarAngles,y .noSwap cpy #0 ; did we just compare against the last depth? bne .innerLoop ; nope -- go back and compare some more beq .outerLoop ; yep -- go back to the outer loop .exit ; ------------------------------------------------------------------------------ ; Erase Bars ; ------------------------------------------------------------------------------ EraseBars subroutine ldx #NumColorLines ; we need to blank out the colors first lda #0 .eraseLoop dex sta LineColor,x ; color be gone! bne .eraseLoop ; done? ; ------------------------------------------------------------------------------ ; Vertical Blanking Code ; ------------------------------------------------------------------------------ VBlank lda INTIM ; wait for the overscan to be done bne VBlank ldx #0 ; set everything up lda #2 sta WSYNC sta VSYNC ; start the vsync sta WSYNC ; first vsync line sta WSYNC ; second vsync line sta WSYNC ; third vsync line stx VSYNC ; turn off vsync lda #44 ; setup the timer sta WSYNC sta TIM64T ; ------------------------------------------------------------------------------ ; Update color table ; ; This routine draws out the copper bars in order of depth from back to front. ; For each bar it sets the appropriate number of lines for the depth and ; position to the color ; ------------------------------------------------------------------------------ DrawBars subroutine lda #$00 ; start with the farthest back bar .barsLoop pha ; save off the current bar index ; ------------------------------------------------------------------------------ ; DrawBar ; ; Draws a single bar -- A points to the offset in the bar table to be drawn ; ------------------------------------------------------------------------------ DrawBar tay ; get the current bar into Y lda BarPositions,y ; get the position of the bar sec sbc BarDepths,y ; subtract off half the lines tax ; save it for later -- this is our vertical pos lda BarColors,y ; get the bar color sta TmpVar ; save it off lda BarDepths,y ; get half the number of lines we need to draw tay ; put it into Y lda TmpVar ; get the color back into A .topLoop sta LineColor - 2,x ; draw the color -- X value is 2 ahead of where we want clc adc #2 ; move to the next color inx ; and the next line dey bne .topLoop ; bottom half of the line sta TmpVar ; save the color pla ; get the current bar index back out again pha ; and save it back for the DrawBars loop tay ; put the index back into Y lda BarDepths,y ; get half the number of lines we need to draw tay ; put it into Y lda TmpVar ; get our color back .bottomLoop sec ; colors are moving down now sbc #2 sta LineColor - 2,x ; draw the color inx ; move to the next line dey bne .bottomLoop pla ; get the current bar value clc ; move the index to the next bar adc #1 cmp NumBars bne .barsLoop ; done? ; ------------------------------------------------------------------------------ ; Kernel code ; ------------------------------------------------------------------------------ Kernel subroutine lda INTIM ; wait until it's time to start drawing bne Kernel sta WSYNC ; we're ready to start sta VBLANK ; turn the display back on ; Top blank section ldx #TopBlankLines ; load the line count .topLoop sta WSYNC ; move to the next line dex ; update line pointer bne .topLoop ; Top section of copper bars only ldx #NumTopLines - 1 ; load the line count .topBarLoop lda LineColor + NumMiddleLines + NumBottomLines,x ; get the background color sta COLUBK dex ; move to the next line index sta WSYNC ; (3 = 0) and wait for the next line to start bne .topBarLoop ; (2 = 2) ; one line of copper bar only -- used to prep for text area lda LineColor + NumMiddleLines + NumBottomLines ; setup the copper bar color for this line sta COLUBK ldx #NumMiddleLines - 1 ; load the line count -- we stop the loop after hitting 0 ldy #(NumMiddleLines - 1) / 8 ; setup the playfield count as well lda LineColor + NumBottomLines,x ; get the next lines color sta WSYNC ; (3 = 0) wait for the next line nop $00 ; (3 = 3) burn 3 cycles to make sure our count matches ; Rotating copper bars and "ATARI 2600" text ; ; background color is stored in RAM, playfield color is based off background ; color. Playfield is stored in table at the end of the ROM. .barLoop sta COLUBK ; (3 = 6) store off the background color ; (loaded at the end of the line) clc ; (2 = 8) adc #$02 ; (2 = 10) get the playfield color sta COLUPF ; (3 = 13) lda PF0FirstTable,y ; (4 = 19) get the value for PF0 sta PF0 ; (3 = 22) lda PF1FirstTable,y ; (4 = 26) get the value for PF1 sta PF1 ; (3 = 29) lda PF2FirstTable,y ; (4 = 31) get the value for PF2 on the left sta PF2 ; (3 = 34) ; safe to write to PF0 after cycle 28 lda PF0SecondTable,y ; (4 = 38) get the value for PF0 sta PF0 ; (3 = 41) ; safe to write to PF1 after cycle 39 lda PF1SecondTable,y ; (4 = 45) get the value for PF1 sta PF1 ; (3 = 47) ; safe to write to PF2 after cycle 50 lda PF2SecondTable,y ; (4 = 51) get the value for PF2 sta PF2 ; (3 = 54) dex ; (2 = 57) move to the next line bmi .exitBarLoop ; (2 = 59) time to be done? txa ; (2 = 61) calculate the offset into the PF data lsr ; (2 = 63) divide by 8 lsr ; (2 = 65) lsr ; (2 = 67) tay ; (2 = 69) stuff it into y lda LineColor + NumBottomLines,x ; (4 = 73) get the background color nop $00 ; (3 = 76/0) burn the 3 remaining cycles to get to the next line jmp .barLoop ; (3 = 3) do it again ; Bottom section of copper bars only .exitBarLoop sta WSYNC ; (3 = 0) finish out the last line of text inx ; (2 = 2) bump X back up to 0 stx PF0 ; (3 = 5) make sure the playfield registers are clear stx PF1 ; (3 = 8) stx PF2 ; (3 = 11) ldx #NumBottomLines ; (3 = 14) load the line count .bottomBarLoop lda LineColor - 1,x ; (4 = 18/9) get the background color sta COLUBK ; (3 = 21/12) sta WSYNC ; (3 = 0) wait for the next line to start dex ; (2 = 2) move to the next line index bne .bottomBarLoop ; (3 = 5) ; Bottom blank section stx COLUBK ; set the background back to black ldx #BottomBlankLines - 1 ; load the line count .bottomLoop sta WSYNC ; move to the next line dex ; update line pointer bne .bottomLoop ; done? ; ------------------------------------------------------------------------------ ; Overscan code ; ------------------------------------------------------------------------------ Overscan subroutine ldx #2 lda #35 ; set the timer to go off in 30 lines sta WSYNC sta TIM64T sta VBLANK ; start up V-Blank jmp MainLoop ; let's do it all again ; ------------------------------------------------------------------------------ ; End of code ; ------------------------------------------------------------------------------ ; starting values for the BarColors and BarAngles variables Bar4StartAngleValues byte $00, $40, $80, $c0 Bar6StartAngleValues byte $00, $2a, $7f, $d4, $55, $aa BarStartColorValues byte $c0, $80, $40, $f0, $60, $20 ; position for the bar, indexed by angle PositionTable byte $30, $30, $31, $32, $33, $34, $35, $36, $37, $38, $39, $3a, $3b, $3c, $3d, $3e byte $3f, $40, $41, $41, $42, $43, $44, $45, $46, $47, $47, $48, $49, $4a, $4a, $4b byte $4c, $4c, $4d, $4e, $4e, $4f, $50, $50, $51, $51, $52, $52, $53, $53, $54, $54 byte $54, $55, $55, $55, $56, $56, $56, $57, $57, $57, $57, $57, $57, $57, $57, $57 byte $58, $57, $57, $57, $57, $57, $57, $57, $57, $57, $56, $56, $56, $55, $55, $55 byte $54, $54, $54, $53, $53, $52, $52, $51, $51, $50, $50, $4f, $4e, $4e, $4d, $4c byte $4c, $4b, $4a, $4a, $49, $48, $47, $47, $46, $45, $44, $43, $42, $41, $41, $40 byte $3f, $3e, $3d, $3c, $3b, $3a, $39, $38, $37, $36, $35, $34, $33, $32, $31, $30 byte $30, $2f, $2e, $2d, $2c, $2b, $2a, $29, $28, $27, $26, $25, $24, $23, $22, $21 byte $20, $1f, $1e, $1e, $1d, $1c, $1b, $1a, $19, $18, $18, $17, $16, $15, $15, $14 byte $13, $13, $12, $11, $11, $10, $0f, $0f, $0e, $0e, $0d, $0d, $0c, $0c, $0b, $0b byte $0b, $0a, $0a, $0a, $09, $09, $09, $08, $08, $08, $08, $08, $08, $08, $08, $08 byte $08, $08, $08, $08, $08, $08, $08, $08, $08, $08, $09, $09, $09, $0a, $0a, $0a byte $0b, $0b, $0b, $0c, $0c, $0d, $0d, $0e, $0e, $0f, $0f, $10, $11, $11, $12, $13 byte $13, $14, $15, $15, $16, $17, $18, $18, $19, $1a, $1b, $1c, $1d, $1e, $1e, $1f byte $20, $21, $22, $23, $24, $25, $26, $27, $28, $29, $2a, $2b, $2c, $2d, $2e, $2f DepthTable byte $07, $07, $07, $07, $06, $06, $06, $05, $05, $04, $04, $03, $03, $03, $03, $03 echo "ROM size =", . - ROMStart org $fffc word Main word Main end