processor 6502 include vcs.h ;=============================================================================== ; A S S E M B L E R - S W I T C H E S ;=============================================================================== NTSC = 1 KOOL_AID_OK = 1 ; disable if console has problems with Kool Aid Man STATIC = 1 ; currently doesn't work! ;=============================================================================== ; C O N S T A N T S ;=============================================================================== INVADER_H = 9 MISSILE_H = 6 ROW_H = INVADER_H+6 NUM_POSITIONS = 11 NUM_ROWS = 5 RAND_EOR_8 = $b2 DX = 0 IF NTSC RED = $40 BLUE = $80 ELSE RED = $60 BLUE = $b0 ENDIF op_nop_imm = $80 op_nop_zp = $04 op_nop_abs = $0c op_nop = $ea op_bit = $24 op_sta = $85 op_lda_zpx = $b5 op_sta_zpx = $95 DUMMY = $2d ;=============================================================================== ; Z P - V A R I A B L E S ;=============================================================================== SEG.U variables ORG $80 RAMKernel ds $30 ; KernelCodeEnd - KernelCode (48 bytes reserved for RAM kernel) ctrlSC = $80 frameCnt .byte random .byte reload .byte tmpVar .byte jmpVec .word position .byte walkDir .byte row .byte tmpColumn .byte yMsl0 .byte yTmpMsl .byte invPat0 .ds NUM_ROWS invPat1 .ds NUM_ROWS ;=============================================================================== ; M A C R O S ;=============================================================================== MAC BIT_B .byte $24 ENDM MAC BIT_W .byte $2c ENDM MAC SLEEP IF {1} = 1 ECHO "ERROR: SLEEP 1 not allowed !" END ENDIF IF {1} & 1 nop $00 REPEAT ({1}-3)/2 nop REPEND ELSE REPEAT ({1})/2 nop REPEND ENDIF ENDM ;=============================================================================== ; M A C R O S ;=============================================================================== MAC DEBUG_BRK IF DEBUG brk ; ENDIF ENDM MAC BIT_B .byte $24 ENDM MAC BIT_W .byte $2c ; 4 cylces ENDM ;=============================================================================== ; R O M - C O D E ;=============================================================================== SEG Bank0 ORG $f000 ;--------------------------------------------------------------- KernelCode SUBROUTINE ; patched into .loop: ; @61..71 PatchInv: lda InvaderTbl-1,y ; 4 PatchHM: sta HMOVE ; 3 @68.. bit DUMMY early HMOVEs! Patch0: sta RESP0 ; 3 @71.. bit DUMMY 1st invader A Patch1: sta RESP1 ; 3 @74.. bit DUMMY 2nd invader A PatchGRP0: sta GRP0 ; 3 lda GRP0 PatchGRP1: sta GRP1 ; 3 lda GRP1 PatchMsl: lda ENABLTbl-1,y ; 4 sta ENABL ; 3 txa ; 2 PatchRESP0: Patch3: sta RESP0 ; 3 @16.. bit DUMMY 1st invader B PatchRESP1: Patch4: sta RESP1 -DX,x ; 4 @20.. lda DUMMY -DX,x 2nd invader B sta RESP0 -DX,x ; 4 @24.. lda RESP0 -DX,x sta RESP1 -DX,x ; 4 lda RESP1 -DX,x sta RESP0 -DX,x ; 4 lda RESP0 -DX,x sta RESP1 -DX,x ; 4 lda RESP1 -DX,x sta RESP0 -DX,x ; 4 lda RESP0 -DX,x sta RESP1 -DX,x ; 4 lda RESP1 -DX,x sta RESP0 -DX,x ; 4 lda RESP0 -DX,x sta RESP1 -DX,x ; 4 lda RESP1 -DX,x sta RESP0 -DX,x ; 4 @56.. lda RESP0 -DX,x dey ; 2 bne .loop ; 2³ jmp ContKernel KernelCodeEnd: PD = KernelCode - RAMKernel Start SUBROUTINE sei ; Disable interrupts, if there are any. cld ; Clear BCD math bit. ldx #0 txs pha ; Set stack to beginning. txa .clearLoop: pha dex bne .clearLoop jsr GameInit .mainLoop: jsr VerticalBlank jsr GameCalc jsr DrawScreen jsr OverScan jmp .mainLoop GameInit SUBROUTINE inc random ldx #$2f .loopCopy: lda KernelCode,x sta RAMKernel,x dex bpl .loopCopy lda #>Delays sta jmpVec+1 lda #1 sta CTRLPF lda #%111111 sta invPat0 lda #%11111 sta invPat1 sta WSYNC SLEEP 45 sta RESBL lda #$80 sta HMBL rts VerticalBlank SUBROUTINE lda #2 sta WSYNC sta VSYNC sta WSYNC sta WSYNC lsr IF NTSC ldx #44-12 ELSE ldx #44+18 ENDIF sta WSYNC sta VSYNC stx TIM64T rts GameCalc SUBROUTINE inc frameCnt lda frameCnt and #$1f bne .skipMove ldx position bit walkDir bmi .negDir inx cpx #NUM_POSITIONS bne .setPos dex dex bne .invDir .negDir: dex bpl .setPos inx inx .invDir: lda walkDir eor #$80 sta walkDir .setPos stx position .skipMove: lda #BLUE|$6 sta COLUPF ldy #$0c ldx #$0c lda #0 bit SWCHB bmi .skipDemo lda #$02 sta COLUPF ldy #RED|$a ldx #BLUE|$a lda #$55 .skipDemo: sty COLUP0 stx COLUP1 sta PF0 sta PF2 asl sta PF1 rts align 256 DrawScreen SUBROUTINE .idxPat = Patch0+1 - PD IF NTSC ldx #227+22 ELSE ldx #227+27 ENDIF .waitTim: lda INTIM bne .waitTim sta WSYNC sta VBLANK stx TIM64T ; IF NTSC ; ldx #10 ; ELSE ; ldx #20 ; ENDIF ;.wait: ; sta WSYNC ; dex ; bne .wait ;--------------------------------------------------------------- ; lda #%01 ; 2 ; sta NUSIZ0 ; 3 ; sta NUSIZ1 ; 3 lda yMsl0 sta yTmpMsl IF STATIC ldx #0 ; ldx #10 ELSE ldx #NUM_ROWS-1 ENDIF .loopColumns: stx row ;***** patch kernel positioning: ***** IF STATIC ldy row ELSE ldy position ENDIF lda HMP0Tbl,y ; 4 sta HMP0 ; 3 lda HMP1Tbl,y ; 4 sta HMP1 ; 3 lda yTmpMsl sec sbc #ROW_H sta yTmpMsl sec sbc #INVADER_H+MISSILE_H bcs .noMissile adc #