371 lines
14 KiB
ArmAsm
371 lines
14 KiB
ArmAsm
; Feature flags
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NO_INTERRUPTS equ 0 ; turn off for crossrunner debugging
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NO_MUSIC equ 1 ; turn music + tool loading off
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; External data space provided by the main program segment
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tiledata EXT
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TileStore EXT
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; Sprite plane data and mask banks are provided as an external segment
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;
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; The sprite data holds a set of pre-rendered sprites that are optimized to support the rendering pipeline. There
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; are four copies of each sprite, along with the cooresponding mask laid out into 4x4 tile regions where the
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; empty row and column is shared between adjacent blocks.
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;
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; Logically, the memory is laid out as 4 columns of sprites and 4 rows.
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;
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; +---+---+---+---+---+---+---+---+---+---+---+---+-...
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; | | | | | | | | | | | | | ...
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; +---+---+---+---+---+---+---+---+---+---+---+---+-...
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; | | 0 | 0 | | 1 | 1 | | 2 | 2 | | 3 | 3 | ...
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; +---+---+---+---+---+---+---+---+---+---+---+---+-...
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; | | 0 | 0 | | 1 | 1 | | 2 | 2 | | 3 | 3 | ...
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; +---+---+---+---+---+---+---+---+---+---+---+---+-...
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; | | | | | | | | | | | | | ...
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; +---+---+---+---+---+---+---+---+---+---+---+---+-...
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; | | 4 | 4 | | 5 | 5 | | 6 | 6 | | 7 | 7 | ...
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; +---+---+---+---+---+---+---+---+---+---+---+---+-...
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; | | 4 | 4 | | 5 | 5 | | 6 | 6 | | 7 | 7 | ...
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; +---+---+---+---+---+---+---+---+---+---+---+---+-...
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; | | | | | | | | | | | | | ...
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; +---+---+---+---+---+---+---+---+---+---+---+---+-...
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;
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; For each sprite, when it needs to be copied into an on-screen tile, it could exist at any offset compared to its
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; natural alignment. By having a buffer around the sprite data, an address pointer can be set to a different origin
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; and a simple 8x8 block copy can cut out the appropriate bit of the sprite. For example, here is a zoomed-in look
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; at a sprite with an offset, O, at (-2,-3). As shown, by selecting an appropriate origin, just the top corner
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; of the sprite data will be copied.
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;
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; +---+---+---+---++---+---+---+---++---+---+---+---++---+---+---+---+..
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; | | || | || | | | || | | | |
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; +---+-- O----------------+ --+---++---+---+---+---++---+---+---+---+..
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; | | | | | || | | | || | | | |
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; +---+-- | | --+---++---+---+---+---++---+---+---+---+..
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; | | | | | || | | | || | | | |
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; +---+-- | | --+---++---+---+---+---++---+---+---+---+..
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; | | | | | || | | | || | | | |
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; +===+== | ++===+== | ==+===++===+===+===+===++===+===+===+===+..
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; | | | || | S | S | S || S | S | S | || | | | |
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; +---+-- +----------------+ --+---++---+---+---+---++---+---+---+---+..
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; | | || S | S S | S || S | S | S | S || | | | |
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; +---+---+---+---++---+---+---+---++---+---+---+---++---+---+---+---+..
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; | | | | || S | S | S | S || S | S | S | S || | | | |
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; +---+---+---+---++---+---+---+---++---+---+---+---++---+---+---+---+..
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; | | | | || S | S | S | S || S | S | S | S || | | | |
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; +===+===+===+===++===+===+===+===++===+===+===+===++===+===+===+===+..
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; | | | | || S | S | S | S || S | S | S | S || | | | |
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; +---+---+---+---++---+---+---+---++---+---+---+---++---+---+---+---+..
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; | | | | || S | S | S | S || S | S | S | S || | | | |
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; +---+---+---+---++---+---+---+---++---+---+---+---++---+---+---+---+..
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; | | | | || S | S | S | S || S | S | S | S || | | | |
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; +---+---+---+---++---+---+---+---++---+---+---+---++---+---+---+---+..
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; | | | | || | S | S | S || S | S | S | || | | | |
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; +---+---+---+---++---+---+---+---++---+---+---+---++---+---+---+---+..
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; . . . . . . . . . . . . . . . . .
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;
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; Each sprite will take up, effectively 9 tiles of storage space per
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; instance (plus edges) and there are 4 instances for the H/V bits
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; and 4 more for the masks. This results in a need for 43,264 bytes
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; for all 16 sprites.
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spritedata EXT
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spritemask EXT
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; Core engine functionality. The idea is that that source file can be PUT into
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; a main source file and all of the functionality will be available.
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;
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; There are some constancts that must be externally defined that can affect how
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; the GTE runtime works
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;
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; NO_MUSIC : Set to non-zero to avoid using any source
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; NO_INTERRUPTS : Set to non-zero to avoid installing custom interrupt handlers
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mx %00
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; Assumes the direct page is set and EngineMode and UserId has been initialized
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_CoreStartUp
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jsr IntStartUp ; Enable certain interrupts
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jsr InitMemory ; Allocate and initialize memory for the engine
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jsr EngineReset ; All of the resources are allocated, put the engine in a known state
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jsr InitGraphics ; Initialize all of the graphics-related data
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jsr InitSprites ; Initialize the sprite subsystem
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jsr InitTiles ; Initialize the tile subsystem
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jsr InitTimers ; Initialize the timer subsystem
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rts
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_CoreShutDown
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jsr IntShutDown
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rts
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; Install interrupt handlers. We use the VBL interrupt to keep animations
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; moving at a consistent rate, regarless of the rendered frame rate. The
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; one-second timer is generally just used for counters and as a handy
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; frames-per-second trigger.
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IntStartUp
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lda #NO_INTERRUPTS
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bne :no_interrupts
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PushLong #0
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pea $0015 ; Get the existing 1-second interrupt handler and save
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_GetVector
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PullLong OldOneSecVec
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pea $0015 ; Set the new handler and enable interrupts
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PushLong #OneSecHandler
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_SetVector
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pea $0006
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_IntSource
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PushLong #VBLTASK ; Also register a Heart Beat Task
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_SetHeartBeat
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:no_interrupts
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rts
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IntShutDown
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lda #NO_INTERRUPTS
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bne :no_interrupts
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pea $0007 ; disable 1-second interrupts
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_IntSource
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PushLong #VBLTASK ; Remove our heartbeat task
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_DelHeartBeat
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pea $0015
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PushLong OldOneSecVec ; Reset the interrupt vector
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_SetVector
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:no_interrupts
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rts
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; Interrupt handlers. We install a heartbeat (1/60th second and a 1-second timer)
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OneSecHandler mx %11
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phb
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pha
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jsr _SetDataBank
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rep #$20
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inc OneSecondCounter
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sep #$20
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ldal $E0C032
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and #%10111111 ;clear IRQ source
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stal $E0C032
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pla
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plb
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clc
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rtl
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mx %00
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; This is OK, it's referenced by a long address
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VBLTASK hex 00000000
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TaskCnt dw 1
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hex 5AA5
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VblTaskCode mx %11
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lda #1
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stal TaskCnt ; Reset the task count
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_VblTaskPatch jml _TaskStub ; Just something to catch the interrupt
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_TaskStub rtl
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mx %00
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; Reset the engine to a known state
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; Blitter initialization
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EngineReset
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stz ScreenHeight
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stz ScreenWidth
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stz ScreenY0
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stz ScreenY1
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stz ScreenX0
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stz ScreenX1
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stz ScreenTileHeight
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stz ScreenTileWidth
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stz StartX
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stz OldStartX
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stz StartXMod164
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stz StartY
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stz OldStartY
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stz StartYMod208
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; stz EngineMode
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stz DirtyBits
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stz LastRender ; Initialize as is a full render was performed
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stz LastPatchOffset
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stz BG1StartX
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stz BG1StartXMod164
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stz BG1StartY
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stz BG1StartYMod208
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stz BG1OffsetIndex
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stz BG0TileOriginX
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stz BG0TileOriginY
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stz OldBG0TileOriginX
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stz OldBG0TileOriginY
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stz BG1TileOriginX
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stz BG1TileOriginY
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stz OldBG1TileOriginX
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stz OldBG1TileOriginY
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stz TileMapWidth
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stz TileMapHeight
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stz TileMapPtr
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stz TileMapPtr+2
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stz FringeMapPtr
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stz FringeMapPtr+2
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stz BG1TileMapWidth
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stz BG1TileMapHeight
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stz BG1TileMapPtr
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stz BG1TileMapPtr+2
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stz CompileBankTop
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stz SCBArrayPtr
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stz SCBArrayPtr+2
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stz SpriteBanks
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stz SpriteMap
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stz ActiveSpriteCount
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stz OneSecondCounter
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lda #13
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sta tmp15
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stz tmp14
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; Rebuild all of the bank blitters
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:loop
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ldx #BlitBuff
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lda #^BlitBuff
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ldy tmp14
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jsr BuildBank
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lda tmp14
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clc
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adc #4
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sta tmp14
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dec tmp15
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bne :loop
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; Set the scanline tables to reasonable default values
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; ldx #{416*2}-2
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; lda #0
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;:sxm_loop
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; sta StartXMod164Arr,x
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; dex
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; dex
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; bpl :sxm_loop
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rts
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WaitForKey sep #$20
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stal KBD_STROBE_REG ; clear the strobe
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:WFK ldal KBD_REG
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bpl :WFK
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rep #$20
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and #$007F
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rts
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ClearKbdStrobe sep #$20
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stal KBD_STROBE_REG
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rep #$20
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rts
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; Read the keyboard and paddle controls and return in a game-controller-like format
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_ReadControl pea $0000 ; low byte = key code, high byte = %------AB
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sep #$20
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ldal OPTION_KEY_REG ; 'B' button
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and #$80
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beq :BNotDown
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lda #>PAD_BUTTON_B
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ora 2,s
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sta 2,s
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:BNotDown
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ldal COMMAND_KEY_REG
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and #$80
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beq :ANotDown
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lda #>PAD_BUTTON_A
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ora 2,s
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sta 2,s
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:ANotDown
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ldal KBD_STROBE_REG ; read the keyboard
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bit #$80
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beq :KbdNotDwn ; check the key-down status
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and #$7f
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ora 1,s
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sta 1,s
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cmp LastKey
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beq :KbdDown
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sta LastKey
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lda #>PAD_KEY_DOWN ; set the keydown flag
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ora 2,s
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sta 2,s
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bra :KbdDown
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:KbdNotDwn
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stz LastKey
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:KbdDown
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rep #$20
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pla
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rts
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; Helper function to take a local pixel coordinate [0, ScreenWidth-1],[0, ScreenHeight-1] and return the
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; row and column in the tile store that is corresponds to. This takes into consideration the StartX and
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; StartY offsets.
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;
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; This is more specialized than the code in the _MarkDirtySprite routine below since it does not deal with
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; negative or off-screen values.
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_OriginToTileStore
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lda StartYMod208
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lsr
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lsr
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and #$FFFE ; Store the pre-multiplied by 2 for indexing
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tay
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lda StartXMod164
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lsr
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and #$FFFE ; Same pre-multiply by 2 for later
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tax
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rts
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; X = local x-coordinate (0, playfield width)
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; Y = local y-coordinate (0, playfield height)
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_LocalToTileStore
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clc
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tya
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adc StartYMod208 ; Adjust for the scroll offset
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cmp #208 ; check if we went too far positive
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bcc *+5
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sbc #208
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lsr
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lsr
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and #$FFFE ; Store the pre-multiplied by 2 for indexing
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tay
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clc
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txa
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adc StartXMod164
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cmp #164
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bcc *+5
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sbc #164
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lsr
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and #$FFFE ; Same pre-multiply by 2 for later
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tax
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rts |