nolist VRAMLINES_C000 equ &2200 org &4000 run $ xor a call &bc0e di ld de,&C008+240 ld hl,VRAMLINES_C000 ;call generate_vram80 ; HL dest(256 aligned), DE vram start generate_vram80 ld c,80 ld a,32 rows25: ex af,af' push de ld b,8 lines8: ld (hl),e:inc h:ld (hl),d:dec h:inc hl ld a,d:add 8:ld d,a dec b jr nz,lines8 pop de ex de,hl:add hl,bc:ex de,hl ex af,af' dec a jr nz,rows25 ld c,32 wat: push bc ld ix,256*16 rdw: ld a,(seed):ld b,a ld a,r:ld a,r:add b:add c:add ixh:ld (seed),a ld hl,(randp) call rand and 3 or a jr nz,no0 inc h jr after no0: dec a jr nz,no1 dec h jr after no1: dec a jr nz,no2 inc l jr after no2: dec l after: ld (randp),hl ld a,l:ld l,h srl l ld b,ixh call putpixel dec ix ld a,ixh:or ixl jr nz,rdw pop bc dec c jr nz,wat ld hl,&c000:ld de,&c001:ld (hl),0:ld bc,16000:ldir ld iy,0 xana: ld c,0 triLoop: ld hl,tri ld a,(nframe+1) cp 3 jr c,no3 ex de,hl add iy,de ex de,hl no3 call rand and 3 cp 3:jr nz,nomod3 xor a nomod3: add a:add l:ld l,a ld a,ixh:add (hl):srl a:ld ixh,a:inc hl ld a,ixl:add (hl):srl a:ld ixl,a add iyl ld l,a ld b,32 ld a,iyh add b ld b,a ld a,ixh add iyl call putpixel dec c jr nz, triLoop ld hl,(nframe):inc hl:ld (nframe),hl ld a,h cp 1 jr c,noL add iy,de noL: jr xana ;loop: ; ld b,&f5 ; vsync0: ; in a,(c) ; rra ; jr c,vsync0 ; ld b,&f5 ; vsync1: ; in a,(c) ; rra ; jr nc,vsync1 ;jr loop ;a=x,l=y,b=col putpixel: ld h,VRAMLINES_C000/256 ld e,(hl):inc h:ld d,(hl) ld l,a:srl l:ld h,0:add hl,de and a,1 jr z,rightPix srl b rightPix: ld a,(hl) xor b ld (hl),a ret ; Fast RND ; ; An 8-bit pseudo-random number generator, ; using a similar method to the Spectrum ROM, ; - without the overhead of the Spectrum ROM. ; ; R = random number seed ; an integer in the range [1, 256] ; ; R -> (33*R) mod 257 ; ; S = R - 1 ; an 8-bit unsigned integer nframe: dw 0 rand: ld a,(seed) ld b, a rrca ; multiply by 32 rrca rrca xor &1f add a, b sbc a, 255 ; carry ld (seed), a ret seed: db 211 randp: db 32,64 tri: db 64,0 db 0,128 db 128,128 list aend: nolist