fire_tiny: load in zero page
This commit is contained in:
Vince Weaver
parent
cfb81b0ec6
commit
c8e0be4dab
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@ -9,7 +9,7 @@ all: fire.dsk
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fire.dsk: FIRE FIRE_TINY HELLO
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$(DOS33) -y fire.dsk SAVE A HELLO
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$(DOS33) -y fire.dsk BSAVE -a 0x1000 FIRE
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$(DOS33) -y fire.dsk BSAVE -a 0x1000 FIRE_TINY
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$(DOS33) -y fire.dsk BSAVE -a 0x70 FIRE_TINY
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####
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@ -23,7 +23,7 @@ fire.o: fire.s gr_fast_clear.s vapor_lock.s \
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####
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FIRE_TINY: fire_tiny.o
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ld65 -o FIRE_TINY fire_tiny.o -C ../linker_scripts/apple2_1000.inc
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ld65 -o FIRE_TINY fire_tiny.o -C ../linker_scripts/apple2_70.inc
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fire_tiny.o: fire_tiny.s
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ca65 -o fire_tiny.o fire_tiny.s -l fire_tiny.lst
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141
fire/fire_tiny.s
141
fire/fire_tiny.s
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@ -5,43 +5,51 @@
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; based on code described here http://fabiensanglard.net/doom_fire_psx/
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; 611 bytes at first
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; 601 bytes -- strip out some unused code6
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; 601 bytes -- strip out some unused code
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; 592 bytes -- don't init screen
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; 443 bytes -- remove more dead code
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; 206 bytes -- no need to clear screen
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; 193 bytes -- un-cycle exact the random16 code
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; 189 bytes -- more optimization of random16 code
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; 161 bytes -- move to 8-bit RNG
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; 152 bytes -- reduce lookup to top half colors (had to remove brown)
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; also changed maroon to pink
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; 149 bytes -- use monitor GR
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; Zero Page
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SEEDL = $4E
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SEEDH = $4F
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TEMP = $FA
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TEMPY = $FB
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TEMP = $00
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TEMPY = $01
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XOR_MAGIC = $7657 ; "vW"
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; 100 = $64
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; Soft Switches
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SET_GR = $C050 ; Enable graphics
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FULLGR = $C052 ; Full screen, no text
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LORES = $C056 ; Enable LORES graphics
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; monitor routines
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GR = $F390
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fire_demo:
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; GR part
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bit LORES ; 4
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bit SET_GR ; 4
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bit FULLGR ; 4
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jsr GR ; 3
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bit FULLGR ; 3
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;==========
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; 6
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; Setup white line on bottom
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lda #$ff
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ldx #39
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lda #$ff ; 2
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ldx #39 ; 2
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white_loop:
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sta $7d0,X ; hline 24 (46+47)
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dex
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bpl white_loop
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sta $7d0,X ; hline 24 (46+47) ; 3
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dex ; 1
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bpl white_loop ; 2
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;============
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; 10
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fire_loop:
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@ -65,11 +73,27 @@ xloop:
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smc1:
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lda $7d0,X
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sta TEMP
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and #$f ; mask off
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and #$7 ; mask off
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tay
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jsr random16
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;=============================
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; random8
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;=============================
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; 8-bit 6502 Random Number Generator
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; Linear feedback shift register PRNG by White Flame
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; http://codebase64.org/doku.php?id=base:small_fast_8-bit_prng
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random8:
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lda SEEDL
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beq doEor
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asl
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beq noEor ; if the input was $80, skip the EOR
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bcc noEor
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doEor: eor #$1d
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noEor: sta SEEDL
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; end inlined RNG
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and #$1
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beq no_change
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@ -91,88 +115,21 @@ smc2:
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dey
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bpl yloop
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jmp fire_loop
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bmi fire_loop
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color_progression:
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.byte 0 ; 0->0
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.byte $88 ; 1->8
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.byte 0 ; 2->0
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.byte 0 ; 3->0
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.byte 0 ; 4->0
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.byte 0 ; 5->0
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.byte 0 ; 6->0
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.byte 0 ; 7->0
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.byte $55 ; 8->5
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.byte $11 ; 9->1
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.byte 0 ; 10->0
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.byte 0 ; 11->0
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.byte 0 ; 12->0
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.byte $99 ; 13->9
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.byte 0 ; 14->0
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.byte $dd ; 15->13
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; 16-bit 6502 Random Number Generator
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; Linear feedback shift register PRNG by White Flame
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; http://codebase64.org/doku.php?id=base:small_fast_16-bit_prng
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;=============================
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; random16
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;=============================
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random16:
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lda SEEDL ; 3
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beq low_zero ; $0000 and $8000 are special values ; 3
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;==========
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; 6
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lownz:
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; -1
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asl SEEDL ; Do a normal shift ; 5
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lda SEEDH ; 3
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rol ; 2
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bcs do_eor ; 3
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bcc no_eor ; 3
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do_eor:
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; high byte is in A
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eor #>XOR_MAGIC ; 2
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sta SEEDH ; 3
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lda SEEDL ; 3
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eor #<XOR_MAGIC ; 2
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sta SEEDL ; 3
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eor_rts:
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rts ; 6
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no_eor:
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sta SEEDH ; 3
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jmp eor_rts ; 3+6
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;===========
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; 20
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low_zero:
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lda SEEDH ; 3
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beq do_eor ; High byte is also zero ; 3
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; so apply the EOR
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ceo: ; -1
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; wasn't zero, check for $8000
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asl ; 2
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beq no_eor ; if $00 is left after the shift; 3
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; then it was $80
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; else, do the EOR based on the carry
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cep:
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bcc no_eor
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bcs do_eor
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.byte $00 ; 8->0 ; 1000 0101
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.byte $bb ; 9->11 ; 1001 0001
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.byte 0 ; 10->0 ; 1010 0000
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.byte $aa ; 11->10 ; 1011 0000
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.byte 0 ; 12->0 ; 1100 0000
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.byte $99 ; 13->9 ; 1101 1001
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.byte $00 ; 14->0 ; 1110 0000
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.byte $dd ; 15->13 ; 1111 1101
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gr_offsets:
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.word $400,$480,$500,$580,$600,$680,$700,$780
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.word $428,$4a8,$528,$5a8,$628,$6a8,$728,$7a8
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.word $450,$4d0,$550,$5d0,$650,$6d0,$750,$7d0
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@ -0,0 +1,12 @@
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MEMORY {
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ZP: start = $00, size = $1A, type = rw;
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RAM: start = $70, size = $8E00, file = %O;
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}
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SEGMENTS {
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CODE: load = RAM, type = ro;
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RODATA: load = RAM, type = ro;
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DATA: load = RAM, type = rw;
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BSS: load = RAM, type = bss, define = yes;
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ZEROPAGE: load = ZP, type = zp;
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}
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