processor 6502
include vcs.h
org $F000
;Variables ------
YPosFromBot = $80;
VisiblePlayerLine = $81;
PICS = $82;
ROLLING_COUNTER = $83;
Graphics_Buffer = $84
YPosFromBotE1 = $85;
VisibleEnemyLine = $86;
VisibleEnemyLineCurrent = $87;
EnemyLineBuffer = $88;
VisiblePlayerLineCurrent = $90;
BG_0 = $91;
BG_1 = $92;
BG_2 = $93;
; Constants ------
playerheight ds #8;
;generic start up stuff...
Start
SEI
CLD
LDX #$FF
TXS
LDA #0
STA ROLLING_COUNTER
STA PICS
STA EnemyLineBuffer
ClearMem
STA 0,X
DEX
BNE ClearMem
LDA #$00 ;start with a black background
STA COLUBK
LDA #$1C ;lets go for bright yellow, the traditional color for happyfaces
STA COLUP0
;Setting some variables...
LDA #80
STA YPosFromBot ;Initial Y Position
STA YPosFromBotE1
LDA #010001 ; 2 cycles
STA BG_0 ; 3 cycles
STA BG_1 ; 3 cycles
STA BG_2 ; 3 cycles
;; Let's set up the sweeping line. as Missile 1
LDA #2
; STA ENAM1 ;enable it
LDA #33
STA COLUP0 ;color it
STA COLUP1 ;color it
LDA #$10
; STA NUSIZ0 ;make it quadwidth (not so thin, that)
STA NUSIZ1 ;make it quadwidth (not so thin, that)
LDA #000000 ; set to not move
STA HMM1 ; of HMM1 sets it to moving
;VSYNC time
MainLoop ;+++++++++++++++++++++++++++The start of a new screen
LDA #0
STA GRP0
STA GRP1
STA PF0
STA PF1
STA PF2
LDA #2
STA VSYNC
STA WSYNC
; for up and down, we INC or DEC
; the Y Position
LDA #010000 ;Down?
BIT SWCHA
BNE SkipMoveDown
INC YPosFromBot
INC YPosFromBotE1
INC YPosFromBotE1
SkipMoveDown
LDA #100000 ;Up?
BIT SWCHA
BNE SkipMoveUp
DEC YPosFromBot
DEC YPosFromBotE1
DEC YPosFromBotE1
SkipMoveUp
; for left and right, we're gonna
; set the horizontal speed, and then do
; a single HMOVE. We'll use X to hold the
; horizontal speed, then store it in the
; appropriate register
;assum horiz speed will be zero
LDX #0
LDA #%01000000 ;Left?
BIT SWCHA
BNE SkipMoveLeft
LDX #$10 ;a 1 in the left nibble means go left
;; moving left, so we need the mirror image
LDA #001000 ;a 1 in D3 of REFP0 says make it mirror
STA REFP0
STA REFP1
SkipMoveLeft
LDA #%10000000 ;Right?
BIT SWCHA
BNE SkipMoveRight
LDX #$F0 ;a -1 in the left nibble means go right...
;; moving right, cancel any mirrorimage
LDA #000000
STA REFP0
STA REFP1
SkipMoveRight
STX HMP0 ;set the move for player 0, not the missile like last time...
STX HMP1 ;set the move for player 0, not the missile like last time...
; see if player and missile collide, and change the background color if so
;just a review...comparisons of numbers always seem a little backwards to me,
;since it's easier to load up the accumulator with the test value, and then
;compare that value to what's in the register we're interested.
;in this case, we want to see if D7 of CXM1P (meaning Player 0 hit
; missile 1) is on. So we put 10000000 into the Accumulator,
;then use BIT to compare it to the value in CXM1P
LDA #%10000000
BIT CXM1P
BEQ NoCollision ;skip if not hitting...
LDA YPosFromBot ;must be a hit! load in the YPos...
STA COLUBK ;and store as the bgcolor
NoCollision
STA CXCLR ;reset the collision detection for next time
STA WSYNC ;//////////////////////////////////////////////
;setup pic animations ----------------------------------------------
INC ROLLING_COUNTER
LDA ROLLING_COUNTER
AND #15 ;every 8th screen swap to next image of player
CMP #8
BEQ PICSET4
JMP PICSET3
PICSET4 LDA PICS
CMP #8
BEQ PICSET
LDA #8
JMP PICSET2
PICSET LDA #0
PICSET2 STA PICS
PICSET3
LDA ROLLING_COUNTER
AND #25 ;how often to move enemy, larger number is slower
CMP #8
BEQ PICSET5
LDA #001111 ; +1 in the left nibble
JMP PICSET6
PICSET5 LDA #011111 ; 0 in the left nibble
PICSET6 STA HMP1 ; of HMP1 sets it to moving the enemy
LDA #8
CLC
ADC PICS ;add value of pics to Accumulator
STA VisibleEnemyLineCurrent
LDA #8
CLC
ADC PICS ;add value of pics to Accumulator
STA VisiblePlayerLineCurrent
;setup pic animations ----------------------------------------------
STA WSYNC ;//////////////////////////////////////////////
LDA #43
STA TIM64T
LDA #0
STA VSYNC
;------------------------- setup backgrounds 20 pixels accross
LDA #255 ; 3 cycles
STA PF0 ; 3 cycles
STA PF1 ; 3 cycles
STA PF2 ; 3 cycles
;-------------------------
WaitForVblankEnd
LDA INTIM
BNE WaitForVblankEnd
LDY #4 ; was 191
STA WSYNC
STA HMOVE
STA VBLANK
;main scanline loop...
PreScanLoop
ScanLoop1 ;start of kernal +++++++++++++++++++++++ for skyline
LDA PFCOLOR-1,Y ; 4 cycles
STA COLUBK ;and store as the bgcolor ; 3 cycles
LDA PFData0-1,Y ; 4 cycles
STA PF0 ; 3 cycles
LDA PFData1-1,Y ; 4 cycles
STA RESM0 ; 3 cycles places left scan line leftmost
STA PF1 ; 3 cycles
LDA PFData2-1,Y ; 4 cycles
STA PF2 ; 3 cycles
LDA #0 ;2 cycles =30
STA GRP1 ; put player 1 into grp1 3 cycles
STA GRP0 ;put that line as player graphic 0 ;3 cycles =28
DEY ;count down number of scan lines 2 cycles =71
STA WSYNC ;3 cycles =74
BNE ScanLoop1 ;2 cycles =76
EndScanLoop1 ;end of kernal +++++++++++++++++++++++ for skyline
LDA #100;
STA COLUBK ;and store as the bgcolor
LDY #186 ; was 191 was 186
LDA #0
STA PF0 ; 3 cycles
STA PF1 ; 3 cycles
STA PF2 ; 3 cycles
LDA #%11100011 ;The last 3 bits control number and size of players
;the firs 3 bits control missle size
STA NUSIZ0
STA NUSIZ1
STA WSYNC ;3 cycles
ScanLoop ;start of kernal +++++++++++++++++++++++ for players
;-------------------------- y register is the line number currently being drawn
; SPRITE DRAW
tya ; 2 Transfers the byte in the Y Register to the Accumulator.
sec ; 2 Sets the carry (C) flag (in the processor Status Register byte).
sbc YPosFromBot ; 3 Subtracts a byte in memory from the byte in the Accumulator, and "borrows" if necessary.
adc #8 ; 2 Adds byte in memory to the byte in the Accumulator, plus the carry flag if set.
bcs .Draw ; 2(3) Branches up to 127 bytes forward or 128 bytes backward from its own address if the carry flag is set.
nop ; 2 Wait
nop ; 2 Wait
sec ; 2 Sets the carry (C) flag
bcs .skipDraw ; 3 Branches up to 127 bytes forward or 128 bytes backward from its own address if the carry flag is set.
.Draw
lda MainPlayerGraphics,y ; 5 Loads the Accumulator with a byte from memory.
sta GRP0 ; 3 Stores the byte in the Accumulator into memory.
.skipDraw
;-->18 cycles used
;--------------------------
; STA GRP0 ;set player graphics 3 cycles
; STA GRP1 ;set player graphics 3 cycles
DEY ;count down number of scan lines 2 cycles =
STA WSYNC ;3 cycles =
BNE ScanLoop ;2 cycles =
EndScanLoop ;end of kernal +++++++++++++++++ for players
STA WSYNC
STA VBLANK
LDX #24
OverScanWait
STA WSYNC
DEX
BNE OverScanWait
JMP MainLoop
MainPlayerGraphics
.byte #010100
.byte #010100
.byte #011000
.byte #011000
.byte #%01111110
.byte #010000
.byte #111000
.byte #111000
SpriteEnd
.byte #100010
.byte #100100
.byte #101000
.byte #011000
.byte #%01111110
.byte #010000
.byte #111000
.byte #111000
EnemyGraphics
.byte #%01111000
.byte #%10000100
.byte #001000
.byte #010000
.byte #010000
.byte #010000
.byte #111000
.byte #111000
.byte #%01111000
.byte #%01001000
.byte #010000
.byte #100000
.byte #100000
.byte #100000
.byte #%01110000
.byte #%01110000
PFData0
.byte #001111
.byte #011111
.byte #%01111111
.byte #%11111111
PFData1
.byte #000000
.byte #001110
.byte #111111
.byte #%01111111
PFData2
.byte #000000
.byte #011000
.byte #%10111100
.byte #%11111111
PFCOLOR
.byte #$5F
.byte #$5D
.byte #$5B
.byte #$59
org $FFFC
.word Start
.word Start
0
What am I doing wrong with skipdraw
Started by yllawwally, Apr 2 2010 5:08 PM
4 replies to this topic
#1 OFFLINE
yllawwally
-
-
- 59 posts
Star Raider
- Location:Corvallis, OR
Posted Fri Apr 2, 2010 5:08 PM
I tried to adapt this code to use skipdraw. However the graphics are not correct. The sprite starts in the correct location, however it seems to scroll through the memory, until you're on a certain y position. Then the graphics continue to the bottom of the screen. My code is below.
#2 OFFLINE
johnon
-
-
- 241 posts
Chopper Commander
- Aspiring 2600 Developer
- Location:South Carolina, US
Posted Fri Apr 2, 2010 5:37 PM
Well, for starters, I'm not sure your graphics are handled correctly. There are a lot of missing % signs in there and I've never seen graphics handled in decimal numbers (usually binary, though in the case of Adventure, hexadecimal), nor have I ever seen any decimal numbers as big as 10000 used in anything Atari VCS. Coupled with the fact that there are zeros in front of those decimal numbers (not needed, as by rules of basic mathematics), this leads me to believe that your issue is that you have, in fact, accidentally messed up some numbers and the VCS is reading it a little oddly. Remember, it won't correct your mistakes. 
If this is, in fact, the issue, it's an easy fix. See if that works. Otherwise, I can't help you, as my knowledge of VCS coding is minimal at this point.
I only say this is the issue, as any number of odd things could happen when you make the smallest mistake. Once, after trying to incorporate editing playfield and background graphics in the same timer, I ended up changing my playfield from white to purple and activating a constant stream of audio without ever knowing what I did wrong.
However, I could always be really off. As I've said, I haven't worked with the system long.
If this is, in fact, the issue, it's an easy fix. See if that works. Otherwise, I can't help you, as my knowledge of VCS coding is minimal at this point.
I only say this is the issue, as any number of odd things could happen when you make the smallest mistake. Once, after trying to incorporate editing playfield and background graphics in the same timer, I ended up changing my playfield from white to purple and activating a constant stream of audio without ever knowing what I did wrong.
However, I could always be really off. As I've said, I haven't worked with the system long.
Edited by johnon, Fri Apr 2, 2010 5:57 PM.
#3 OFFLINE
yllawwally
-
-
- 59 posts
Star Raider
- Location:Corvallis, OR
Posted Mon Apr 5, 2010 12:12 PM
I don't know what happened to the graphics info. In the original source, it's all in binary. Something about pasting it here, damaged it.
processor 6502
include vcs.h
org $F000
;Variables ------
YPosFromBot = $80;
VisiblePlayerLine = $81;
PICS = $82;
ROLLING_COUNTER = $83;
Graphics_Buffer = $84
YPosFromBotE1 = $85;
VisibleEnemyLine = $86;
VisibleEnemyLineCurrent = $87;
EnemyLineBuffer = $88;
VisiblePlayerLineCurrent = $90;
BG_0 = $91;
BG_1 = $92;
BG_2 = $93;
; Constants ------
playerheight ds #8;
;generic start up stuff...
Start
SEI
CLD
LDX #$FF
TXS
LDA #0
STA ROLLING_COUNTER
STA PICS
STA EnemyLineBuffer
ClearMem
STA 0,X
DEX
BNE ClearMem
LDA #$00 ;start with a black background
STA COLUBK
LDA #$1C ;lets go for bright yellow, the traditional color for happyfaces
STA COLUP0
;Setting some variables...
LDA #80
STA YPosFromBot ;Initial Y Position
STA YPosFromBotE1
LDA #010001 ; 2 cycles
STA BG_0 ; 3 cycles
STA BG_1 ; 3 cycles
STA BG_2 ; 3 cycles
;; Let's set up the sweeping line. as Missile 1
LDA #2
; STA ENAM1 ;enable it
LDA #33
STA COLUP0 ;color it
STA COLUP1 ;color it
LDA #$10
; STA NUSIZ0 ;make it quadwidth (not so thin, that)
STA NUSIZ1 ;make it quadwidth (not so thin, that)
LDA #000000 ; set to not move
STA HMM1 ; of HMM1 sets it to moving
;VSYNC time
MainLoop ;+++++++++++++++++++++++++++The start of a new screen
LDA #0
STA GRP0
STA GRP1
STA PF0
STA PF1
STA PF2
LDA #2
STA VSYNC
STA WSYNC
; for up and down, we INC or DEC
; the Y Position
LDA #010000 ;Down?
BIT SWCHA
BNE SkipMoveDown
INC YPosFromBot
INC YPosFromBotE1
INC YPosFromBotE1
SkipMoveDown
LDA #100000 ;Up?
BIT SWCHA
BNE SkipMoveUp
DEC YPosFromBot
DEC YPosFromBotE1
DEC YPosFromBotE1
SkipMoveUp
; for left and right, we're gonna
; set the horizontal speed, and then do
; a single HMOVE. We'll use X to hold the
; horizontal speed, then store it in the
; appropriate register
;assum horiz speed will be zero
LDX #0
LDA #%01000000 ;Left?
BIT SWCHA
BNE SkipMoveLeft
LDX #$10 ;a 1 in the left nibble means go left
;; moving left, so we need the mirror image
LDA #001000 ;a 1 in D3 of REFP0 says make it mirror
STA REFP0
STA REFP1
SkipMoveLeft
LDA #%10000000 ;Right?
BIT SWCHA
BNE SkipMoveRight
LDX #$F0 ;a -1 in the left nibble means go right...
;; moving right, cancel any mirrorimage
LDA #000000
STA REFP0
STA REFP1
SkipMoveRight
STX HMP0 ;set the move for player 0, not the missile like last time...
STX HMP1 ;set the move for player 0, not the missile like last time...
; see if player and missile collide, and change the background color if so
;just a review...comparisons of numbers always seem a little backwards to me,
;since it's easier to load up the accumulator with the test value, and then
;compare that value to what's in the register we're interested.
;in this case, we want to see if D7 of CXM1P (meaning Player 0 hit
; missile 1) is on. So we put 10000000 into the Accumulator,
;then use BIT to compare it to the value in CXM1P
LDA #%10000000
BIT CXM1P
BEQ NoCollision ;skip if not hitting...
LDA YPosFromBot ;must be a hit! load in the YPos...
STA COLUBK ;and store as the bgcolor
NoCollision
STA CXCLR ;reset the collision detection for next time
STA WSYNC ;//////////////////////////////////////////////
;setup pic animations ----------------------------------------------
INC ROLLING_COUNTER
LDA ROLLING_COUNTER
AND #15 ;every 8th screen swap to next image of player
CMP #8
BEQ PICSET4
JMP PICSET3
PICSET4 LDA PICS
CMP #8
BEQ PICSET
LDA #8
JMP PICSET2
PICSET LDA #0
PICSET2 STA PICS
PICSET3
LDA ROLLING_COUNTER
AND #25 ;how often to move enemy, larger number is slower
CMP #8
BEQ PICSET5
LDA #001111 ; +1 in the left nibble
JMP PICSET6
PICSET5 LDA #011111 ; 0 in the left nibble
PICSET6 STA HMP1 ; of HMP1 sets it to moving the enemy
LDA #8
CLC
ADC PICS ;add value of pics to Accumulator
STA VisibleEnemyLineCurrent
LDA #8
CLC
ADC PICS ;add value of pics to Accumulator
STA VisiblePlayerLineCurrent
;setup pic animations ----------------------------------------------
STA WSYNC ;//////////////////////////////////////////////
LDA #43
STA TIM64T
LDA #0
STA VSYNC
;------------------------- setup backgrounds 20 pixels accross
LDA #255 ; 3 cycles
STA PF0 ; 3 cycles
STA PF1 ; 3 cycles
STA PF2 ; 3 cycles
;-------------------------
WaitForVblankEnd
LDA INTIM
BNE WaitForVblankEnd
LDY #4 ; was 191
STA WSYNC
STA HMOVE
STA VBLANK
;main scanline loop...
PreScanLoop
ScanLoop1 ;start of kernal +++++++++++++++++++++++ for skyline
LDA PFCOLOR-1,Y ; 4 cycles
STA COLUBK ;and store as the bgcolor ; 3 cycles
LDA PFData0-1,Y ; 4 cycles
STA PF0 ; 3 cycles
LDA PFData1-1,Y ; 4 cycles
STA RESM0 ; 3 cycles places left scan line leftmost
STA PF1 ; 3 cycles
LDA PFData2-1,Y ; 4 cycles
STA PF2 ; 3 cycles
LDA #0 ;2 cycles =30
STA GRP1 ; put player 1 into grp1 3 cycles
STA GRP0 ;put that line as player graphic 0 ;3 cycles =28
DEY ;count down number of scan lines 2 cycles =71
STA WSYNC ;3 cycles =74
BNE ScanLoop1 ;2 cycles =76
EndScanLoop1 ;end of kernal +++++++++++++++++++++++ for skyline
LDA #100;
STA COLUBK ;and store as the bgcolor
LDY #186 ; was 191 was 186
LDA #0
STA PF0 ; 3 cycles
STA PF1 ; 3 cycles
STA PF2 ; 3 cycles
LDA #%11100011 ;The last 3 bits control number and size of players
;the firs 3 bits control missle size
STA NUSIZ0
STA NUSIZ1
STA WSYNC ;3 cycles
ScanLoop ;start of kernal +++++++++++++++++++++++ for players
;-------------------------- y register is the line number currently being drawn
; SPRITE DRAW
tya ; 2 Transfers the byte in the Y Register to the Accumulator.
sec ; 2 Sets the carry (C) flag (in the processor Status Register byte).
sbc YPosFromBot ; 3 Subtracts a byte in memory from the byte in the Accumulator, and "borrows" if necessary.
adc #8 ; 2 Adds byte in memory to the byte in the Accumulator, plus the carry flag if set.
bcs .Draw ; 2(3) Branches up to 127 bytes forward or 128 bytes backward from its own address if the carry flag is set.
nop ; 2 Wait
nop ; 2 Wait
sec ; 2 Sets the carry (C) flag
lda MainPlayerGraphics,y ; 5 Loads the Accumulator with a byte from memory.
bcs .skipDraw ; 3 Branches up to 127 bytes forward or 128 bytes backward from its own address if the carry flag is set.
.Draw
sta GRP0 ; 3 Stores the byte in the Accumulator into memory.
.skipDraw
;-->18 cycles used
;--------------------------
skipDrawRight ; 3 from BCC
LDA #0 ; 2
BEQ continueRight ; 3 Return...
; STA GRP0 ;set player graphics 3 cycles
; STA GRP1 ;set player graphics 3 cycles
TXA ; 2 A-> Current scannline
SEC ; 2 Set Carry
SBC YPosFromBot ; 3
ADC #8 ; 2 calc if sprite is drawn
BCC skipDrawRight ; 2/3 To skip or not to skip?
TAY ; 2
lda P1Graphic,y ; 4
continueRight:
STA GRP0
DEY ;count down number of scan lines 2 cycles =
STA WSYNC ;3 cycles =
BNE ScanLoop ;2 cycles =
EndScanLoop ;end of kernal +++++++++++++++++ for players
STA WSYNC
STA VBLANK
LDX #24
OverScanWait
STA WSYNC
DEX
BNE OverScanWait
JMP MainLoop
MainPlayerGraphics
.byte #010100
.byte #010100
.byte #011000
.byte #011000
.byte #%01111110
.byte #010000
.byte #111000
.byte #111000
SpriteEnd
.byte #100010
.byte #100100
.byte #101000
.byte #011000
.byte #%01111110
.byte #010000
.byte #111000
.byte #111000
EnemyGraphics
.byte #%01111000
.byte #%10000100
.byte #001000
.byte #010000
.byte #010000
.byte #010000
.byte #111000
.byte #111000
.byte #%01111000
.byte #%01001000
.byte #010000
.byte #100000
.byte #100000
.byte #100000
.byte #%01110000
.byte #%01110000
PFData0
.byte #001111
.byte #011111
.byte #%01111111
.byte #%11111111
PFData1
.byte #000000
.byte #001110
.byte #111111
.byte #%01111111
PFData2
.byte #000000
.byte #011000
.byte #%10111100
.byte #%11111111
PFCOLOR
.byte #$5F
.byte #$5D
.byte #$5B
.byte #$59
org $FFFC
.word Start
.word Start
#4 OFFLINE
yllawwally
-
-
- 59 posts
Star Raider
- Location:Corvallis, OR
Posted Mon Apr 5, 2010 12:15 PM
OK I'll just insert a file. Apparently paste doesn't like, binary numbers? And the uploader doesn't like .asm files.
Attached Files
-
wallyface8.txt 8.96K
32 downloads
#5 OFFLINE
Omegamatrix
-
-
- 4,795 posts
River Patroller
- Location:Oh, Canada
Posted Mon Apr 5, 2010 1:47 PM
The forum software is gobbling up % signs followed by a 0. This bug has been reported though.
I usually just take the .asm file and zip it before posting. That's what most other people seem to do too.
I usually just take the .asm file and zip it before posting. That's what most other people seem to do too.
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