Primordial Ooze Posted February 22, 2009 Share Posted February 22, 2009 I'm trying to get a missile to fire from the player 0 when the fire button is pressed. I managed to get the missile to appear when the player presses the fire button, but it doesn't appear where expected at the front of player 0. Additionally if player 0 moves the missile doesn't fire at player 0's new position. Any ideas? ; First we have to tell DASM that we're ; coding to the 6502: processor 6502 ; Then we have to include the "vcs.h" file ; that includes all the "convenience names" ; for all the special atari memory locations... include "vcs.h" include "macro.h" ;************************************************************************** SEG.U vars; tells dasm that the proceding instructions are variable declarations ORG $80; tells dasm to start placing our variables in memory location 0080 player0x = $80; player0's x position player0y = $81; player0's y position shotfired = $82 visibleplayer0line = $83; current visible line for player 0 player0buffer = $84; player buffer for holding the line to draw for the player graphic missile0x = $85; missile 0's x position missile0y = $86; missile 0's y position visiblemissileline = $87; line where missile is drawn lives = $88; player lives score = $89; game score SEG code ; tell DASM where in the memory to place ; all the code that follows...$F000 is the preferred ; spot where it goes to make an atari program ORG $F000 ; we'll call the start of our program "Start". Start SEI ; Disable Any Interrupts CLD ; Clear BCD math bit. LDX #$FF; put X to the top... TXS ; ...and use it reset the stack pointer ; Clear RAM and all TIA registers lda #0 ;Put Zero into A, X is at $FF Clear sta 0,x ;Now, this doesn't mean what you think... dex ;decrement X (decrease X by one) bne Clear;if the last command resulted in something ;that's "N"ot "Equal" to Zero, branch back ;to "Clear" ;--------------------- ; One Time Initiations lda #$FA sta COLUBK; set the background color to sandy brown lda #$04 sta COLUP0; set the player color to silver lda #$B8 sta COLUPF; set the playfield color to ooze green ;--------------------- ; Start New Game StartNewGame lda #105 sta player0x; player0's initial x position lda #40 sta player0y; player0's initial y position lda #0 sta shotfired; set shotfired inital value to 0 lda #0 sta missile0x; missile 0's initial x position lda #0 sta missile0y; missile 0's initial y position lda #3 sta lives; start the player with 3 lives lda #0 sta score; set high bit of score inital value to 0 lda #0 sta score+1; set nibble bit of score inital value to 0 lda #0 sta score+2; low bit of score inital value to 0 GameLoop ;*********************** VERTICAL SYNC HANDLER lda #2 sta VSYNC; Sync it up you damn dirty television! ; and that vsync on needs to be held for three scanlines... ; count with me here, sta WSYNC; one... (our program waited for the first scanline to finish...) sta WSYNC; two... sta WSYNC; three... lda #43;load 43 (decimal) in the accumulator sta TIM64T;and store that in the timer lda #0 ; Zero out the VSYNC sta VSYNC ; cause that time is over ;*********************** Joystick Input ; Here we check for left and right ; joystick input lda #%01000000; a 0 in bit D6 means the joystick was pushed left bit SWCHA; was the joystick moved left? bne SkipPlayer0MoveLeft; if bit D6 isn't equal to 0 then jump to SkipPlayer0MoveLeft dec player0x; otherwise the player moved the joystick left so deincrement the players position by one SkipPlayer0MoveLeft lda #%10000000; a 0 in bit D7 means the joystick was pushed right bit SWCHA ; was the joystick moved right? bne SkipPlayer0MoveRight;if bit D6 isn't equal to 0 then jump to SkipPlayer0MoveRight inc player0x;otherwise the player moved the joystick right so increment the players position by one SkipPlayer0MoveRight ldx player0x; load the players position into the x register jsr PositionSprite; jump to our Position Sprite Subroutine to position the player lda #0 ; zero out the buffer sta player0buffer; just in case lda INPT4; read button input bmi ButtonNotPressed; skip if button not pressed lda #1 ; must be pressed, set accumulator to 1 (true) sta shotfired; shotFired to true from value in acumulator lda player0x; load player 0's x position sta missile0x; and set it to the missile 0's x position lda player0y; load player 0's y position sta missile0y; and set it to missile 0's y position lda #2 ; set the acumulator to 2 sed ; set decimal mode clc ; clear carry status adc missile0y; set missile 0's position just above player 0 cld ; clear decimal mode ButtonNotPressed ;*********************** VERTICAL BLANK WAIT-ER WaitForVblankEnd lda INTIM;load timer... BNE WaitForVblankEnd;killing time if the timer's not yet zero ldy #191 ;Y is going to hold how many lines we have to do ;...we're going to count scanlines here. theoretically ; since this example is ass simple, we could just repeat ; the timer trick, but often its important to know ; just what scan line we're at. sta WSYNC;We do a WSYNC just before that so we don't turn on sta VBLANK;End the VBLANK period with the zero ;*********************** Scan line Loop ScanLoop sta WSYNC ;Wait for the previous line to finish lda player0buffer;buffer was set during last scanline sta GRP0 ;put it as graphics now cpy player0y; compare the player's y position bne SkipActivatePlayer0; if it isn't 0 then jump to SkipActivePlayer0 lda #5 ; otherwise load our accumulatior with the number of lines to draw sta visibleplayer0line; and store it SkipActivatePlayer0 ;set player buffer to all zeros for this line, and then see if ;we need to load it with graphic data lda #0 sta player0buffer ;set buffer, not GRP0 ;if the VisiblePlayerLine is non zero, ;we're drawing it next line ldx visibleplayer0line;check the visible player line... beq FinishPlayer;skip the drawing if its zero... lda player0-1,X ;otherwise, load the correct line from player0 ;section below... it's off by 1 though, since at zero ;we stop drawing sta player0buffer;put that line as player graphic for the next line dec visibleplayer0line;and decrement the line count FinishPlayer ; here the idea is that VisibleMissileLine ; is zero if the line isn't being drawn now, ; otherwise it's however many lines we have to go CheckActivateMissile cpy missile0y bne SkipActivateMissile lda #8 sta visiblemissileline SkipActivateMissile ;turn missile off then see if it's turned on lda #0 sta ENAM0 ;if the VisibleMissileLine is non zero, ;we're drawing it lda visiblemissileline beq FinishMissile lda #2 sta ENAM0 dec visiblemissileline inc missile0y FinishMissile dey ;subtract one off the line counter thingy bne ScanLoop;and repeat if we're not finished with all the scanlines. lda #2 ;#2 for the VBLANK... sta WSYNC ;Finish this final scanline. sta VBLANK ; Make TIA output invisible for the overscan, ; (and keep it that way for the vsync and vblank) ;***************************** OVERSCAN CALCULATIONS ;I'm just gonna count off the 30 lines of the overscan. ;You could do more program code if you wanted to. ldx #30 ;store 30 OverScanWait sta WSYNC dex bne OverScanWait jmp GameLoop ;Continue this loop forver! Back to the code for the vsync etc Divide15 .POS SET 0 ; start our counter at 0 REPEAT 256 ; repeat this loop 256 times .byte (.POS / 15) + 1; put that counter value / 15 in the ROM .POS SET .POS + 1 ; increment our counter by one REPEND ; repeat the loop if neccessary PositionSprite sta WSYNC ; wait for vsync ; Pass X register holding desired X position of sprite! lda Divide15,x; xPosition / 15 tax ; transfer the value in the accumulator to the x register SimpleLoop dex ; deincrement x by 1 bne SimpleLoop; continue looping if the x register isn't 0 sta RESP0; start drawing the sprite rts ; return from the subroutine ; here's the actual player0 graphic player0 .byte #%00011000 .byte #%00111100 .byte #%11111111 .byte #%00111100 .byte #%00011000 update_low_score_digits sed ; set decimal mode clc ; clear carry status adc score ; add accumulator to score's low digits w/carry. sta score; store the updated low digits. ;NOTE: Here's where a triple-NOP comes into play. We need ;a seperate entrypoint to this subroutine for cases where the ;low digits are ignored (like adding 100, for example). But ;carry status and BCD mode need to have been setup. So, ;place the triple-NOP opcode here to skip over them... ;with A reset at zero so that only carry affects the score: lda #0 ; reset the accumulator... .byte $0C ; ...and skip over the next 2 bytes update_middle_score_digits sed ; set decimal mode clc; clear carry status adc score+1 ; add accumulator to score's middle digits w/carry. sta score+1 ; store the updated middle digits ;Here we do the same thing (in case the game needs to add 10,000... ;or 100,000 increments to a score (ignoring all the lower ones) ;Again, A is reset at zero so that only carry affects the score: lda #0 ; reset the accumulator... .byte $0C; ...and skip over the next 2 bytes update_high_score_digits sed ; set decimal mode clc ; clear carry status adc score+1; add accumulator to score's high digits w/carry. sta score+2; store the last 2 digits ;With the score updated, clear BCD mode and exit via RTS: cld ; clear decimal mode rts ; and return to the program line that called this routine. ;************************************************************************* ; Interrupt Vectors ORG $FFFA InterruptVectors .word Start ; NMI .word Start ; RESET .word Start ; IRQ END Quote Link to comment Share on other sites More sharing options...
Rybags Posted February 22, 2009 Share Posted February 22, 2009 I'm not up to scratch on the 2600, but... lda player0y; load player 0's y position sta missile0y; and set it to missile 0's y position lda #2 ; set the acumulator to 2 sed ; set decimal mode clc ; clear carry status adc missile0y; set missile 0's position just above player 0 cld ; clear decimal mode ButtonNotPressed ;*********************** VERTICAL BLANK WAIT-ER WaitForVblankEnd lda INTIM;load timer... Why are you using Decimal mode for calculating Y postition? Also, you're doing the add, but not storing it anywhere. Another unrelated hint... with flags, rather than testing them by doing a LDA... BEQ - it's useful to just use the top 2 bits of a byte to signify things, then you can just test with the BIT instruction, without having to lose contents of a register. Quote Link to comment Share on other sites More sharing options...
Primordial Ooze Posted February 23, 2009 Author Share Posted February 23, 2009 (edited) Thanks, i fixed the code and now i got it to appear above the player sprite. However for some reason it doesn't fire from player 0's x position and instead fires from the same exact location every time. I have posted the code for reference. ; First we have to tell DASM that we're ; coding to the 6502: processor 6502 ; Then we have to include the "vcs.h" file ; that includes all the "convenience names" ; for all the special atari memory locations... include "vcs.h" include "macro.h" ;************************************************************************** SEG.U vars; tells dasm that the proceding instructions are variable declarations ORG $80; tells dasm to start placing our variables in memory location 0080 player0x = $80; player0's x position player0y = $81; player0's y position visibleplayer0line = $82; current visible line for player 0 player0buffer = $83; player buffer for holding the line to draw for the player graphic missile0x = $84; missile 0's x position missile0y = $85; missile 0's y position visiblemissile0line = $86; line where missile is drawn lives = $87; player lives score = $88; game score SEG code ; tell DASM where in the memory to place ; all the code that follows...$F000 is the preferred ; spot where it goes to make an atari program ORG $F000 ; we'll call the start of our program "Start". Start SEI ; Disable Any Interrupts CLD ; Clear BCD math bit. LDX #$FF; put X to the top... TXS ; ...and use it reset the stack pointer ; Clear RAM and all TIA registers lda #0 ;Put Zero into A, X is at $FF Clear sta 0,x ;Now, this doesn't mean what you think... dex ;decrement X (decrease X by one) bne Clear;if the last command resulted in something ;that's "N"ot "Equal" to Zero, branch back ;to "Clear" ;--------------------- ; One Time Initiations lda #$FA sta COLUBK; set the background color to sandy brown lda #$04 sta COLUP0; set the player color to silver lda #$B8 sta COLUPF; set the playfield color to ooze green ;--------------------- ; Start New Game StartNewGame lda #105 sta player0x; player0's initial x position lda #40 sta player0y; player0's initial y position lda #0 sta missile0x; missile 0's initial x position lda #0 sta missile0y; missile 0's initial y position lda #3 sta lives; start the player with 3 lives lda #0 sta score; set high bit of score inital value to 0 lda #0 sta score+1; set nibble bit of score inital value to 0 lda #0 sta score+2; low bit of score inital value to 0 GameLoop ;*********************** VERTICAL SYNC HANDLER lda #2 sta VSYNC; Sync it up you damn dirty television! ; and that vsync on needs to be held for three scanlines... ; count with me here, sta WSYNC; one... (our program waited for the first scanline to finish...) sta WSYNC; two... sta WSYNC; three... lda #43;load 43 (decimal) in the accumulator sta TIM64T;and store that in the timer lda #0 ; Zero out the VSYNC sta VSYNC ; cause that time is over ;*********************** Joystick Input ; Here we check for left and right ; joystick input lda #%01000000; a 0 in bit D6 means the joystick was pushed left bit SWCHA; was the joystick moved left? bne SkipPlayer0MoveLeft; if bit D6 isn't equal to 0 then jump to SkipPlayer0MoveLeft dec player0x; otherwise the player moved the joystick left so deincrement the players position by one SkipPlayer0MoveLeft lda #%10000000; a 0 in bit D7 means the joystick was pushed right bit SWCHA ; was the joystick moved right? bne SkipPlayer0MoveRight;if bit D6 isn't equal to 0 then jump to SkipPlayer0MoveRight inc player0x;otherwise the player moved the joystick right so increment the players position by one SkipPlayer0MoveRight ldx player0x; load the players position into the x register jsr PositionSprite; jump to our Position Sprite Subroutine to position the player lda #0 ; zero out the buffer sta player0buffer; just in case lda INPT4; read button input bmi ButtonNotPressed; skip if button not pressed lda player0x; load player 0's x position sta missile0x; and set it to the missile 0's x position lda player0y; load player 0's y position sta missile0y; and set it to missile 0's y position lda #8 ; set the acumulator to 8 clc ; clear carry status adc missile0y; add 2 to missile 0's y position so it's above player 0 sta missile0y; and set it to missile 0's y position ButtonNotPressed ;*********************** VERTICAL BLANK WAIT-ER WaitForVblankEnd lda INTIM;load timer... BNE WaitForVblankEnd;killing time if the timer's not yet zero ldy #191 ;Y is going to hold how many lines we have to do ;...we're going to count scanlines here. theoretically ; since this example is ass simple, we could just repeat ; the timer trick, but often its important to know ; just what scan line we're at. sta WSYNC;We do a WSYNC just before that so we don't turn on sta VBLANK;End the VBLANK period with the zero ;*********************** Scan line Loop ScanLoop sta WSYNC ;Wait for the previous line to finish lda player0buffer;buffer was set during last scanline sta GRP0 ;put it as graphics now cpy player0y; compare the player's y position bne SkipActivatePlayer0; if it isn't 0 then jump to SkipActivePlayer0 lda #5 ; otherwise load our accumulatior with the number of lines to draw sta visibleplayer0line; and store it SkipActivatePlayer0 ;set player buffer to all zeros for this line, and then see if ;we need to load it with graphic data lda #0 sta player0buffer ;set buffer, not GRP0 ;if the VisiblePlayerLine is non zero, ;we're drawing it next line ldx visibleplayer0line;check the visible player line... beq FinishPlayer;skip the drawing if its zero... lda player0-1,X ;otherwise, load the correct line from player0 ;section below... it's off by 1 though, since at zero ;we stop drawing sta player0buffer;put that line as player graphic for the next line dec visibleplayer0line;and decrement the line count FinishPlayer ; here the idea is that visiblemissile0line ; is zero if the line isn't being drawn now, ; otherwise it's however many lines we have to go CheckActivateMissile cpy missile0y; is missile 0's y position the same as the current scanline? bne SkipActivateMissile; if it isn't then don't set missle 0's visible lines lda #8 ; otherwise set the missiles visible lines to 8 sta visiblemissile0line; and store it in the visiblemissileline SkipActivateMissile ;turn missile off then see if it's turned on lda #0 sta ENAM0; disable the missile ;if the visiblemissile0line is non zero, ;we're drawing it lda visiblemissile0line; if the visiblemissle line is zero beq FinishMissile; don't draw the missile lda #2 ; otherwise set the accumulator to 2 sta ENAM0 ; and draw the missile dec visiblemissile0line; and decrement the visiblemissileline by 1 inc missile0y ; increment missle 0's y position by 1 FinishMissile dey ;subtract one off the line counter thingy bne ScanLoop;and repeat if we're not finished with all the scanlines. lda #2 ;#2 for the VBLANK... sta WSYNC ;Finish this final scanline. sta VBLANK ; Make TIA output invisible for the overscan, ; (and keep it that way for the vsync and vblank) ;***************************** OVERSCAN CALCULATIONS ;I'm just gonna count off the 30 lines of the overscan. ;You could do more program code if you wanted to. ldx #30 ;store 30 OverScanWait sta WSYNC dex bne OverScanWait jmp GameLoop ;Continue this loop forver! Back to the code for the vsync etc Divide15 .POS SET 0 ; start our counter at 0 REPEAT 256 ; repeat this loop 256 times .byte (.POS / 15) + 1; put that counter value / 15 in the ROM .POS SET .POS + 1 ; increment our counter by one REPEND ; repeat the loop if neccessary PositionSprite sta WSYNC ; wait for vsync ; Pass X register holding desired X position of sprite! lda Divide15,x; xPosition / 15 tax ; transfer the value in the accumulator to the x register SimpleLoop dex ; deincrement x by 1 bne SimpleLoop; continue looping if the x register isn't 0 sta RESP0; start drawing the sprite rts ; return from the subroutine ; here's the actual player0 graphic player0 .byte #%00011000 .byte #%00111100 .byte #%11111111 .byte #%00111100 .byte #%00011000 update_low_score_digits sed ; set decimal mode clc ; clear carry status adc score ; add accumulator to score's low digits w/carry. sta score; store the updated low digits. ;NOTE: Here's where a triple-NOP comes into play. We need ;a seperate entrypoint to this subroutine for cases where the ;low digits are ignored (like adding 100, for example). But ;carry status and BCD mode need to have been setup. So, ;place the triple-NOP opcode here to skip over them... ;with A reset at zero so that only carry affects the score: lda #0 ; reset the accumulator... .byte $0C ; ...and skip over the next 2 bytes update_middle_score_digits sed ; set decimal mode clc; clear carry status adc score+1 ; add accumulator to score's middle digits w/carry. sta score+1 ; store the updated middle digits ;Here we do the same thing (in case the game needs to add 10,000... ;or 100,000 increments to a score (ignoring all the lower ones) ;Again, A is reset at zero so that only carry affects the score: lda #0 ; reset the accumulator... .byte $0C; ...and skip over the next 2 bytes update_high_score_digits sed ; set decimal mode clc ; clear carry status adc score+1; add accumulator to score's high digits w/carry. sta score+2; store the last 2 digits ;With the score updated, clear BCD mode and exit via RTS: cld ; clear decimal mode rts ; and return to the program line that called this routine. ;************************************************************************* ; Interrupt Vectors ORG $FFFA InterruptVectors .word Start ; NMI .word Start ; RESET .word Start ; IRQ END Sincerely, Primordial Ooze Edited February 23, 2009 by Primordial Ooze Quote Link to comment Share on other sites More sharing options...
Wickeycolumbus Posted February 23, 2009 Share Posted February 23, 2009 (edited) Your problem is that you never reposition the missile. No matter what you store in missile x, it will never move horizontally. You should probably get write/find a universal horizontal positioning routine. this is the one I use: PositionSprites sta HMCLR sec sta WSYNC PositionSpriteLoop sbc #15 bcs PositionSpriteLoop eor #7 asl asl asl asl sta.wx HMP0,X sta RESP0,X sta WSYNC sta HMOVE rts all you do is load the horizontal position to the accumulator, load the sprite # in X (0 for P0, 1 for P1, 2 for M0, 3 for M1, 4 for BL), and jsr PositionSprites. it takes 2 lines, and you have to put a WSYNC write in between calls like this: lda player0x ldx #0 jsr PositionSprites sta WSYNC lda missile0x ldx #2 jsr PositionSprites the WSYNC write is required because of a hardware bug of the TIA that requires a 24 cycle delay after an HMOVE before HMxx writes. It will work fine on an emulator without the WSYNC write, but there will be unpredictable results on the real thing. Edited February 23, 2009 by Wickeycolumbus Quote Link to comment Share on other sites More sharing options...
Primordial Ooze Posted February 23, 2009 Author Share Posted February 23, 2009 (edited) Thanks, but it still doesn't quite work. If you hold the fire button down and move the player towards the left after you reach the middle left you will notice missile 0 will "cave in" into player 0's sprite and if you continue moving left the missile will be almost completely merged with player 0's sprite and stops working altogether. If you move towards the right, everything works as normal. Any ideas? ; First we have to tell DASM that we're ; coding to the 6502: processor 6502 ; Then we have to include the "vcs.h" file ; that includes all the "convenience names" ; for all the special atari memory locations... include "vcs.h" include "macro.h" ;************************************************************************** SEG.U vars; tells dasm that the proceding instructions are variable declarations ORG $80; tells dasm to start placing our variables in memory location 0080 player0x = $80; player0's x position player0y = $81; player0's y position visibleplayer0line = $82; current visible line for player 0 player0buffer = $83; player buffer for holding the line to draw for the player graphic missile0x = $84; missile 0's x position missile0y = $85; missile 0's y position visiblemissile0line = $86; line where missile is drawn lives = $87; player lives score = $88; game score SEG code ; tell DASM where in the memory to place ; all the code that follows...$F000 is the preferred ; spot where it goes to make an atari program ORG $F000 ; we'll call the start of our program "Start". Start SEI; Disable Any Interrupts CLD ; Clear BCD math bit. LDX #$FF; put X to the top... TXS; ...and use it reset the stack pointer ; Clear RAM and all TIA registers lda #0;Put Zero into A, X is at $FF Clear sta 0,x;Now, this doesn't mean what you think... dex;decrement X (decrease X by one) bne Clear;if the last command resulted in something ;that's "N"ot "Equal" to Zero, branch back ;to "Clear" ;--------------------- ; One Time Initiations lda #$FA sta COLUBK; set the background color to sandy brown lda #$04 sta COLUP0; set the player color to silver lda #$B8 sta COLUPF; set the playfield color to ooze green ;--------------------- ; Start New Game StartNewGame lda #105 sta player0x; player0's initial x position lda #40 sta player0y; player0's initial y position lda #0 sta missile0x; missile 0's initial x position lda #0 sta missile0y; missile 0's initial y position lda #3 sta lives; start the player with 3 lives lda #0 sta score; set high bit of score inital value to 0 lda #0 sta score+1; set nibble bit of score inital value to 0 lda #0 sta score+2; low bit of score inital value to 0 GameLoop ;*********************** VERTICAL SYNC HANDLER lda #2 sta VSYNC; Sync it up you damn dirty television! ; and that vsync on needs to be held for three scanlines... ; count with me here, sta WSYNC; one... (our program waited for the first scanline to finish...) sta WSYNC; two... sta WSYNC; three... lda #43;load 43 (decimal) in the accumulator sta TIM64T;and store that in the timer lda #0; Zero out the VSYNC sta VSYNC; cause that time is over ;*********************** Joystick Input ; Here we check for left and right ; joystick input lda #%01000000; a 0 in bit D6 means the joystick was pushed left bit SWCHA; was the joystick moved left? bne SkipPlayer0MoveLeft; if bit D6 isn't equal to 0 then jump to SkipPlayer0MoveLeft dec player0x; otherwise the player moved the joystick left so deincrement the players position by one SkipPlayer0MoveLeft lda #%10000000; a 0 in bit D7 means the joystick was pushed right bit SWCHA; was the joystick moved right? bne SkipPlayer0MoveRight;if bit D6 isn't equal to 0 then jump to SkipPlayer0MoveRight inc player0x;otherwise the player moved the joystick right so increment the players position by one SkipPlayer0MoveRight lda player0x; load the players position into the accumulator ldx #0; set the sprite to be positioned as player 0 jsr PositionSprite; jump to our Position Sprite Subroutine to position player 0 sta WSYNC; wait for sync lda #0; zero out the buffer sta player0buffer; just in case lda INPT4; read button input bmi ButtonNotPressed; skip if button not pressed lda player0x; load player 0's x position sta missile0x; and set it to the missile 0's x position lda #4; set the acumulator to 4 clc; clear carry status adc missile0x; add 4 to missile 0's x position so it's centered at player 0 sta missile0x; and set it to missile 0's x position lda player0y; load player 0's y position sta missile0y; and set it to missile 0's y position lda #8; set the acumulator to 8 clc; clear carry status adc missile0y; add 8 to missile 0's y position so it's above player 0 sta missile0y; and set it to missile 0's y position lda missile0x; load missile 0's x position into the accumulator ldx #2; set the sprite to be positioned to missile 0 jsr PositionSprite; jump to our Position Sprite Subroutine to position missile 0 ButtonNotPressed ;*********************** VERTICAL BLANK WAIT-ER WaitForVblankEnd lda INTIM;load timer... BNE WaitForVblankEnd;killing time if the timer's not yet zero ldy #191;Y is going to hold how many lines we have to do ;...we're going to count scanlines here. theoretically ; since this example is ass simple, we could just repeat ; the timer trick, but often its important to know ; just what scan line we're at. sta WSYNC;We do a WSYNC just before that so we don't turn on sta VBLANK;End the VBLANK period with the zero ;*********************** Scan line Loop ScanLoop sta WSYNC;Wait for the previous line to finish lda player0buffer;buffer was set during last scanline sta GRP0;put it as graphics now cpy player0y; compare the player's y position bne SkipActivatePlayer0; if it isn't 0 then jump to SkipActivePlayer0 lda #5; otherwise load our accumulatior with the number of lines to draw sta visibleplayer0line; and store it SkipActivatePlayer0 ;set player buffer to all zeros for this line, and then see if ;we need to load it with graphic data lda #0 sta player0buffer;set buffer, not GRP0 ;if the VisiblePlayerLine is non zero, ;we're drawing it next line ldx visibleplayer0line;check the visible player line... beq FinishPlayer;skip the drawing if its zero... lda player0-1,X;otherwise, load the correct line from player0 ;section below... it's off by 1 though, since at zero ;we stop drawing sta player0buffer;put that line as player graphic for the next line dec visibleplayer0line;and decrement the line count FinishPlayer ; here the idea is that visiblemissile0line ; is zero if the line isn't being drawn now, ; otherwise it's however many lines we have to go CheckActivateMissile cpy missile0y; is missile 0's y position the same as the current scanline? bne SkipActivateMissile; if it isn't then don't set missle 0's visible lines lda #8; otherwise set the missiles visible lines to 8 sta visiblemissile0line; and store it in the visiblemissileline SkipActivateMissile ;turn missile off then see if it's turned on lda #0 sta ENAM0; disable the missile ;if the visiblemissile0line is non zero, ;we're drawing it lda visiblemissile0line; if the visiblemissle line is zero beq FinishMissile; don't draw the missile lda #2; otherwise set the accumulator to 2 sta ENAM0; and draw the missile dec visiblemissile0line; and decrement the visiblemissileline by 1 inc missile0y; increment missle 0's y position by 1 FinishMissile dey;subtract one off the line counter thingy bne ScanLoop;and repeat if we're not finished with all the scanlines. lda #2;#2 for the VBLANK... sta WSYNC;Finish this final scanline. sta VBLANK; Make TIA output invisible for the overscan, ; (and keep it that way for the vsync and vblank) ;***************************** OVERSCAN CALCULATIONS ;I'm just gonna count off the 30 lines of the overscan. ;You could do more program code if you wanted to. ldx #30;store 30 OverScanWait sta WSYNC dex bne OverScanWait jmp GameLoop;Continue this loop forver! Back to the code for the vsync etc PositionSprite sta HMCLR sec sta WSYNC PositionSpriteLoop sbc #15 bcs PositionSpriteLoop eor #7 asl asl asl asl sta.wx HMP0,X sta RESP0,X sta WSYNC sta HMOVE rts ; here's the actual player0 graphic player0 .byte #%00011000 .byte #%00111100 .byte #%11111111 .byte #%00111100 .byte #%00011000 update_low_score_digits sed; set decimal mode clc; clear carry status adc score; add accumulator to score's low digits w/carry. sta score; store the updated low digits. ;NOTE: Here's where a triple-NOP comes into play. We need ;a seperate entrypoint to this subroutine for cases where the ;low digits are ignored (like adding 100, for example). But ;carry status and BCD mode need to have been setup. So, ;place the triple-NOP opcode here to skip over them... ;with A reset at zero so that only carry affects the score: lda #0; reset the accumulator... .byte $0C; ...and skip over the next 2 bytes update_middle_score_digits sed; set decimal mode clc; clear carry status adc score+1; add accumulator to score's middle digits w/carry. sta score+1; store the updated middle digits ;Here we do the same thing (in case the game needs to add 10,000... ;or 100,000 increments to a score (ignoring all the lower ones) ;Again, A is reset at zero so that only carry affects the score: lda #0; reset the accumulator... .byte $0C; ...and skip over the next 2 bytes update_high_score_digits sed; set decimal mode clc; clear carry status adc score+1; add accumulator to score's high digits w/carry. sta score+2; store the last 2 digits ;With the score updated, clear BCD mode and exit via RTS: cld; clear decimal mode rts; and return to the program line that called this routine. ;************************************************************************* ; Interrupt Vectors ORG $FFFA InterruptVectors .word Start ; NMI .word Start ; RESET .word Start ; IRQ END Sincerely, Primordial Ooze PrimordialOoze.bin Edited February 23, 2009 by Primordial Ooze Quote Link to comment Share on other sites More sharing options...
Omegamatrix Posted February 23, 2009 Share Posted February 23, 2009 Primordial Ooze, you can also save some bytes like this: StartNewGame lda #105 sta player0x; player0's initial x position lda #40 sta player0y; player0's initial y position lda #3 sta lives; start the player with 3 lives lda #0 sta missile0x; missile 0's initial x position sta missile0y; missile 0's initial y position sta score; set high bit of score inital value to 0 sta score+1; set nibble bit of score inital value to 0 sta score+2; low bit of score inital value to 0 Because you don't need to reload the accumulator with #0 every time. You can also move all the registers you need to zero out beside each other and put it in a loop: ldx #5 ; number of times through loop lda #0 ; value to be stored .loopClearRam sta missile0x,X ; all the regsiters have been lined up in ram before hand dex ; decrease X bne .loopClearRam ; this loop is taken until X = 0 I presume later on StartNewGame will be used when the reset switch is hit. As it is right now though registers have already been cleared in the intial clear ram and all TIA registers. There are certain ram locations that are more beneficial to link side by side then others, particularly the ones that hold your position values. Quote Link to comment Share on other sites More sharing options...
Primordial Ooze Posted February 23, 2009 Author Share Posted February 23, 2009 Primordial Ooze, you can also save some bytes like this: StartNewGame lda #105 sta player0x; player0's initial x position lda #40 sta player0y; player0's initial y position lda #3 sta lives; start the player with 3 lives lda #0 sta missile0x; missile 0's initial x position sta missile0y; missile 0's initial y position sta score; set high bit of score inital value to 0 sta score+1; set nibble bit of score inital value to 0 sta score+2; low bit of score inital value to 0 Because you don't need to reload the accumulator with #0 every time. You can also move all the registers you need to zero out beside each other and put it in a loop: ldx #5 ; number of times through loop lda #0 ; value to be stored .loopClearRam sta missile0x,X; all the regsiters have been lined up in ram before hand dex ; decrease X bne .loopClearRam ; this loop is taken until X = 0 I presume later on StartNewGame will be used when the reset switch is hit. As it is right now though registers have already been cleared in the intial clear ram and all TIA registers. There are certain ram locations that are more beneficial to link side by side then others, particularly the ones that hold your position values. Thanks, i will do that. Any solutions to my problem? Sincerely, Primordial Ooze Quote Link to comment Share on other sites More sharing options...
Rybags Posted February 23, 2009 Share Posted February 23, 2009 I believe you also need a flag to test if a missile is already onscreen. Otherwise, your code might keep initiating the missile fire because the button is held. You might try using the Missile X-Pos. Just have it set at 0 to signify that no missile is onscreen. Then all you need to do is test the X-Pos before your button checking code. If X-Pos is non-zero, then skip the button check. Of course, you'll need to set Missile X-Pos back to 0 once it's no longer needed. Quote Link to comment Share on other sites More sharing options...
Primordial Ooze Posted February 23, 2009 Author Share Posted February 23, 2009 I believe you also need a flag to test if a missile is already onscreen. Otherwise, your code might keep initiating the missile fire because the button is held. You might try using the Missile X-Pos. Just have it set at 0 to signify that no missile is onscreen. Then all you need to do is test the X-Pos before your button checking code. If X-Pos is non-zero, then skip the button check. Of course, you'll need to set Missile X-Pos back to 0 once it's no longer needed. Actually i can do it using missile0y, as as soon as missile0y hits 0 it stops moving and being drawn. The other problem i am having is the missile "caving in" and merging with the player sprite when you move the player towards the left. Any ideas on why this is happening? Sincerely, Primordial Ooze Quote Link to comment Share on other sites More sharing options...
Primordial Ooze Posted February 25, 2009 Author Share Posted February 25, 2009 I still haven't found a problem with my missile merging with the player sprite and i have tried everything. Any ideas? Sincerely, Primordial Ooze Quote Link to comment Share on other sites More sharing options...
Devin Posted February 25, 2009 Share Posted February 25, 2009 You could explicitly align all the players and missiles during vertical blank. Here is some excellent assembly code that I found on these boards a while ago. I don't know the original authors name. This subroutine will position any of the graphical objects on the screen in the specified column. You just need to assign the registers and JSR. Just note that the HMOVE is not cleared after the call. You need to clear it after horizontal blank is over. ;--------------------------------------------------------------- ; Subroutine: PosSprite ; ; In : a = position. ; x = sprite (0 = player 0, 1 = player 1, ; 2 = missile 0, 3 = missile 1, 4 = ball) ; ; Out : None ; ; Destroyed: A ;--------------------------------------------------------------- PosSprite STA HMCLR SEC STA WSYNC ; begin line 1 PosSpriteLoop SBC #15 BCS PosSpriteLoop ;+4/5 4/ 9.../54 EOR #7 ;+2 6/11.../56 ASL ASL ASL ASL ;+8 14/19.../64 STA.wx HMP0,X ;+5 19/24.../69 STA RESP0,X ;+4 23/28/33/38/43/48/53/58/63/68/73 STA WSYNC ;+3 0 begin line 2 STA HMOVE ;+3 RTS ;+6 9 Quote Link to comment Share on other sites More sharing options...
Wickeycolumbus Posted February 26, 2009 Share Posted February 26, 2009 Your problem is that in your kernel, you enable the missile too late in the line, so on the left side of the screen, the missile wont move vertically. Here is a fixed source and binary. ooze.zip Quote Link to comment Share on other sites More sharing options...
Primordial Ooze Posted February 26, 2009 Author Share Posted February 26, 2009 (edited) Your problem is that in your kernel, you enable the missile too late in the line, so on the left side of the screen, the missile wont move vertically. Here is a fixed source and binary. Thanks for fixing my code. What i don't understand is what you mean by drawing it "late on the scanline". I'm using modified code from the joystick example in Atari 2600 Programming 101 and couldn't figure out what i did wrong. Could you please explain it? Sincerely, Primordial Ooze Edited February 26, 2009 by Primordial Ooze Quote Link to comment Share on other sites More sharing options...
Wickeycolumbus Posted February 26, 2009 Share Posted February 26, 2009 Your problem is that in your kernel, you enable the missile too late in the line, so on the left side of the screen, the missile wont move vertically. Here is a fixed source and binary. Thanks for fixing my code. What i don't understand is what you mean by drawing it "late on the scanline". I'm using modified code from the joystick example in Atari 2600 Programming 101 and couldn't figure out what i did wrong. Could you please explain it? Sincerely, Primordial Ooze In a 2600 kernel, you are storing to the graphics registers just cycles before they are drawn on the screen. Your kernel was attempting to enable the Missile sprite on a pixel that had already been drawn by the time your kernel enabled it. Hope that makes more sense. -Rick Quote Link to comment Share on other sites More sharing options...
Primordial Ooze Posted February 27, 2009 Author Share Posted February 27, 2009 Your problem is that in your kernel, you enable the missile too late in the line, so on the left side of the screen, the missile wont move vertically. Here is a fixed source and binary. Thanks for fixing my code. What i don't understand is what you mean by drawing it "late on the scanline". I'm using modified code from the joystick example in Atari 2600 Programming 101 and couldn't figure out what i did wrong. Could you please explain it? Sincerely, Primordial Ooze In a 2600 kernel, you are storing to the graphics registers just cycles before they are drawn on the screen. Your kernel was attempting to enable the Missile sprite on a pixel that had already been drawn by the time your kernel enabled it. Hope that makes more sense. -Rick Now that i looked at my code and your code side by side, i see what you mean. In my game missile0 always had a higher scanline then player0, however in my game code it always drew player0 first and then the missile which the scanline was already passed through. So to fix my code you just moved my missile code to the beginning of the scanline loop so missile0 is drawn first and then then player0 like it should. Thanks for the explaination, it makes alot of sense! Sincerely, Primordial Ooze Quote Link to comment Share on other sites More sharing options...
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