Is it possible to print a character in Mode 2 in less than a raster line time (64nops)?
YES, using RES and SET commands to calculate next line screen address!!
This routine works in all vertical positions. It automatically calculates from which raster line of character we start to plot (CRTC reg. 9) and it uses special routine for each (0 - 7 lines).
Code is MAXAM compatible / timed and documented to my best..
;FASTEST CHARACTER PRINTER IN ALL Y COORDINATES ;takes less time than a raster line per char. in mode 2 ;9.10.2016 ;FG Brain org &7000 : RUN $ :nolist ;INPUT HL = Screen Address to PLOT ld a,h and %00111000 rra rra ; A=no of raster line (0-7) of char. we plot ;[ rra NEEDED but destroyed then with add a,a ] ld hl,tablinerout ld b,0:ld c,a add hl,bc ld de,jphere+1 ldi:ldi LD DE,&C850 LD BC,font adr ld hl,0 jphere jp jphere ;get adr to jump according to A ret tablinerout dw line0,line1,line2,line3,line4,line5,line6,line7 ;===PLOT 8 BYTES VERTICAL FROM ALL LINES=== ;input DE = &C850 BC=font adr HL=screen adr to print char.font line0 ;LINE 0 ld a,(bc):ld(hl),a:inc c ;5 set 3,h:ld a,(bc):ld(hl),a:inc c ;7 set 4,h:res 3,h:ld a,(bc):ld(hl),a:inc c ;9 set 3,h:ld a,(bc):ld(hl),a:inc c ;7 set 5,h:res 4,h:res 3,h:ld a,(bc):ld(hl),a:inc c ;11 set 3,h:ld a,(bc):ld(hl),a:inc c ;7 set 4,h:res 3,h:ld a,(bc):ld(hl),a:inc c ;9 set 3,h:ld a,(bc):ld(hl),a ;6 RET ;3 ;=64 NOPs line1 ;LINE 1 ld a,(bc):ld(hl),a:inc c ;5 res 3,h:set 4,h:ld a,(bc):ld(hl),a:inc c ;9 set 3,h:ld a,(bc):ld(hl),a:inc c ;7 set 5,h:res 4,h:res 3,h:ld a,(bc):ld(hl),a:inc c ;11 set 3,h:ld a,(bc):ld(hl),a:inc c ;7 res 3,h:set 4,h:ld a,(bc):ld(hl),a:inc c ;9 set 3,h:ld a,(bc):ld(hl),a:inc c ;7 add hl,de:ld a,(bc):ld(hl),a ;7 ret ;3 ;=65 NOPs line2 ;LINE 2 ld a,(bc):ld(hl),a:inc c ;5 set 3,h:ld a,(bc):ld(hl),a:inc c ;7 set 5,h:res 4,h:res 3,h:ld a,(bc):ld(hl),a:inc c ;11 set 3,h:ld a,(bc):ld(hl),a:inc c ;7 set 4,h:res 3,h:ld a,(bc):ld(hl),a:inc c ;9 set 3,h:ld a,(bc):ld(hl),a:inc c ;7 add hl,de:ld a,(bc):ld(hl),a:inc c ;8 set 3,h:ld a,(bc):ld(hl),a ;6 Ret ;3 ;=63 NOPs line3 ;LINE 3 ld a,(bc):ld(hl),a:inc c ;5 set 5,h:res 4,h:res 3,h:ld a,(bc):ld(hl),a:inc c ;11 set 3,h:ld a,(bc):ld(hl),a:inc c ;7 set 4,h:res 3,h:ld a,(bc):ld(hl),a:inc c ;9 set 3,h:ld a,(bc):ld(hl),a:inc c ;7 add hl,de:ld a,(bc):ld(hl),a:inc c ;8 set 3,h:ld a,(bc):ld(hl),a:inc c ;7 set 4,h:res 3,h:ld a,(bc):ld(hl),a ;8 ret ;3 ;=65 NOPs line4 ;LINE 4 ld a,(bc):ld(hl),a:inc c ;5 set 3,h:ld a,(bc):ld(hl),a:inc c ;7 set 4,h:res 3,h:ld a,(bc):ld(hl),a:inc c ;9 set 3,h:ld a,(bc):ld(hl),a:inc c ;7 add hl,de:ld a,(bc):ld(hl),a:inc c ;8 set 3,h:ld a,(bc):ld(hl),a:inc c ;7 set 4,h:res 3,h:ld a,(bc):ld(hl),a:inc c ;9 set 3,h:ld a,(bc):ld(hl),a ;6 ret ;3 ;=61 NOPs line5 ;LINE 5 ld a,(bc):ld(hl),a:inc c ;5 set 4,h:res 3,h:ld a,(bc):ld(hl),a:inc c ;9 set 3,h:ld a,(bc):ld(hl),a:inc c ;7 add hl,de:ld a,(bc):ld(hl),a:inc c ;8 set 3,h:ld a,(bc):ld(hl),a:inc c ;7 set 4,h:res 3,h:ld a,(bc):ld(hl),a:inc c ;9 set 3,h:ld a,(bc):ld(hl),a:inc c ;7 set 5,h:res 4,h:res 3,h:ld a,(bc):ld(hl),a ;10 ret ;3 ;=65 NOPs line6 ;LINE 6 ld a,(bc):ld(hl),a:inc c ;5 set 3,h:ld a,(bc):ld(hl),a:inc c ;7 add hl,de:ld a,(bc):ld(hl),a:inc c ;8 set 3,h:ld a,(bc):ld(hl),a:inc c ;7 set 4,h:res 3,h:ld a,(bc):ld(hl),a:inc c ;9 set 3,h:ld a,(bc):ld(hl),a:inc c ;7 set 5,h:res 4,h:res 3,h:ld a,(bc):ld(hl),a:inc c ;11 set 3,h:ld a,(bc):ld(hl),a ;6 ret ;3 ;=63 NOPs line7 ;LINE 7 ld a,(bc):ld(hl),a:inc c ;5 add hl,de:ld a,(bc):ld(hl),a:inc c ;8 set 3,h:ld a,(bc):ld(hl),a:inc c ;7 set 4,h:res 3,h:ld a,(bc):ld(hl),a:inc c ;9 set 3,h:ld a,(bc):ld(hl),a:inc c ;7 set 5,h:res 4,h:res 3,h:ld a,(bc):ld(hl),a:inc c ;11 set 3,h:ld a,(bc):ld(hl),a:inc c ;7 set 4,h:res 3,h:ld a,(bc):ld(hl),a ;8 ret ;3 ;=65 NOPs align 256 FONT DB 200,100,200,100,200,100,200,100 end
Compare with the normal routine (but much smaller in size), which needs at least 104 nops!!
ldi: ;5 dec hl ;2 ld a,h:add 8:ld h,a ;4 jr nc,okk ;2 / 3 13*8=104 NOPs ld bc,&c050 ; 3 add hl,bc ; 3 jr okk ;3 ; 104+9=113 nops