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Subject: Re: [stella] 13 chars C64-style From: Andrew Towers <mariofrog@xxxxxxxxxxx> Date: Wed, 10 Dec 2003 05:19:49 +1100 |
Still not enough for a whole line, but maybe someone else finds some more cycles. :-)
I rearranged the code again and added a text terminator so I could use a BNE to exit the loop, instead of the DEC-BMI-JMP sequence, saving 5 cycles. There were 8 cycles of code that seemed to have no effect on the final output! The 6-pairs encoding loop was crossing a page boundary, taking an extra 5 cycles. We had 59 spare already, bringing us up to 77 :)
Regards, Andrew.
Attachment:
13ch4.bin
Description: Binary data
;---------------------------------------------------------------------------
;
; Generic 2600 Game
;
;---------------------------------------------------------------------------
processor 6502
include vcs.h
;---------------------------------------------------------------------------
; Constants
;---------------------------------------------------------------------------
;---------------------------------------------------------------------------
; RAM Variables
;---------------------------------------------------------------------------
chara equ $80
charb equ $85
charc equ $8a
chard equ $8f
chare equ $94
charf equ $99
charg equ $9e
chars equ $a2
temp equ $a4
line equ $a5
count equ $a6
textptr equ $a7
savesp equ $a8
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
MAC TEXTDISP
lda charg+{1} ;3
sta ENAM0 ;3
lsr ;2
sta ENAM1 ;3
lsr ;2
sta ENABL ;3
lda charf+{1} ;3
sta GRP0 ;3
lda chare+{1} ;3
sta.w GRP1 ;4
ldx #$26+{2} ;2
nop ;2
nop ;2
stx COLUP0 ;3
stx COLUP1 ;3
lda chard+{1} ;3
sta GRP0 ;3
lda charc+{1} ;3
ldy charb+{1} ;3
stx COLUPF ;3
ldx chara+{1} ;3
sta GRP1 ;3
sty GRP0 ;3
stx GRP1 ;3
sta GRP0 ;3
lda #$20 ;2
sta COLUPF ;3
ENDM
;---------------------------------------------------------------------------
;---------------------------------------------------------------------------
org $F000
;---------------------------------------------------------------------------
;---------------------------------------------------------------------------
;---------------------------------------------------------------------------
; Start of Program
;---------------------------------------------------------------------------
; Clear memory, locate character graphics positions and such,
; initialize key memory values, start GameLoop.
;-------------------------------------------------------------
Start
sei
cld
ldx #$FF
txs
lda #0
clear
sta 0,x
dex
bne clear
;---------------------------------------------------------------------------
; Initialize variables / registers
;---------------------------------------------------------------------------
lda #$48
sta COLUP0
lda #$99
sta COLUP1
lda #255
sta PF0
sta PF1
lda #0
sta PF2
lda #%00000101
sta WSYNC
sta CTRLPF
sta GRP0
sta GRP1
lda #$03 ; set both players to 3 copies
sta NUSIZ0
sta NUSIZ1
lda #$01 ; set vertical delay on for both players
sta VDELP0
sta $2d ; nop
sta RESM0
sta RESM1
sta VDELP1
sta RESBL
sta RESP0
sta RESP1
lda #%11110000
sta HMP1
lda #%11100000
sta HMP0
lda #%10000000
sta HMBL
lda #%10110000
sta HMM0
lda #%01010000
sta HMM1
sta WSYNC
sta HMOVE
;--------------------------------------------------------------------------
; GameLoop
;--------------------------------------------------------------------------
GameLoop
jsr VSync ;start vertical retrace
jsr VBlank ; spare time during screen blank
jsr Picture ; draw one screen
jsr overscan ; do overscan
jmp GameLoop ;back to top
;--------------------------------------------------------------------------
; VSync
;--------------------------------------------------------------------------
VSync
lda #2 ;bit 1 needs to be 1 to start retrace
sta VSYNC ;start retrace
sta WSYNC ;wait a few lines
sta WSYNC
lda #44 ;prepare timer to exit blank period (44)
sta TIM64T ;turn it on
sta WSYNC ;wait one more
sta VSYNC ;done with retrace, write 0 to bit 1
rts ; VSync
;--------------------------------------------------------------------------
; VBlank
;--------------------------------------------------------------------------
; Game Logic
;--------------------------------------------------------------------------
VBlank
rts ; VBlank
;--------------------------------------------------------------------------
; Overscan
;--------------------------------------------------------------------------
; More Game Logic
;--------------------------------------------------------------------------
overscan
sta WSYNC
lda #$00
sta COLUBK
lda #36 ; Use the timer to make sure overscan takes (34)
sta TIM64T ; 30 scan lines. 29 scan lines * 76 = 2204 / 64 = 34.4
endOS
lda INTIM ; We finished, but wait for timer
bne endOS ; by looping till zero
sta WSYNC ; End last scanline
lda #$82
sta VBLANK
lda #$02
sta VBLANK
rts ; overscan
;--------------------------------------------------------------------------
; Draw TV Pictures
;--------------------------------------------------------------------------
;
;--------------------------------------------------------------------------
Picture
pictureLoop
lda INTIM ;check timer for end of VBLANK period
bne pictureLoop ;loop until it reaches 0
sta WSYNC
lda #$80
sta VBLANK ;end screen blank
; Set playfield color
lda #$20
sta COLUPF
lda #15
sta line
lda #0
sta textptr
tsx
stx savesp
SLEEP 46
jmp mainTextLoop ;3
; put this here so we can jump out of the main text loop
; using a 2-cycle relative branch.
quitTextLoop
lda #0
sta GRP0
sta GRP1
sta GRP0
sta GRP1
sta ENAM0
sta ENAM1
sta ENABL
; restore stack pointer
ldx savesp
txs
ldx #11
ScanLoop
sta WSYNC
dex
bne ScanLoop
sta COLUPF
rts ; Picture
;------------------------------------------------------------------
align 256
mainTextLoop
; set up the stack for building screen data
ldx #chars ;2
txs ;2
; load the first text character
; note: x and y are reversed!
ldy textptr ;3
ldx text,y ;4
beq quitTextLoop ;2 ->4 ; look for terminating character (0)
iny ;2
; build screen data for first character
lda fontlo,x ;4
pha ;3
lda fontlo+1,x ;4
pha ;3
lda fontlo+2,x ;4
pha ;3
lda fontlo+3,x ;4
pha ;3
lda fontlo+4,x ;4
pha ;3
; loop through the remaining 6 character pairs
textLineLoop
; load the next two text characters
ldx text,y ;4
lda text1,y ;4
iny ;2
sty textptr ;3
tay ;2
; build screen data for next two characters
lda fonthi,x ;4
ora fontlo,y ;4
pha ;3
lda fonthi+1,x ;4
ora fontlo+1,y ;4
pha ;3
lda fonthi+2,x ;4
ora fontlo+2,y ;4
pha ;3
lda fonthi+3,x ;4
ora fontlo+3,y ;4
pha ;3
lda fonthi+4,x ;4
ora fontlo+4,y ;4
pha ;3
; next character pair
ldy textptr ;3
tsx ;2
bmi textLineLoop ;2
; now render it asap
;;sta WSYNC
;;SLEEP 77 ; 15+23+12
;lda #255 ;2 didn't seem to have any effect ;)
;sta GRP0 ;3
;sta GRP1 ;3 [59]
TEXTDISP 0,0
TEXTDISP 1,2
TEXTDISP 2,4
TEXTDISP 3,6
TEXTDISP 4,8
lda #0 ;2
sta COLUP0 ;3
sta COLUP1 ;3
;sta GRP0
;sta GRP1
;sta GRP0
;sta ENAM0
;sta ENAM1
sta.w ENABL ;4 use up one extra cycle left over!
jmp mainTextLoop ;3
;------------------------------------------------------------------
;------------------------------------------------------------------
;---------------------------------------------------------------------------
; note: dasm doesn't like using x or y as a label!
align 256
text
byte t ,h ,r ,e ,n ,h ,r
byte _ ,_ ,_ ,e ,o ,ast,_
byte eq ,eq ,eq ,eq ,eq ,eq ,eq
byte t ,h ,s ,i ,_ ,_ ,_
byte w ,h ,l ,_ ,u ,c ,_
byte o ,f ,s ,u ,f ,i ,a
byte w ,r ,t ,n ,_ ,o ,_
byte t ,e ,t ,t ,e ,n ,w
byte t ,e ,t ,r ,u ,i ,e
byte i ,s ,i ,_ ,o ,_ ,_
byte ast,ast,e ,yy ,c ,o ,ast
byte yy ,e ,_ ,t ,i ,_ ,_
byte a ,c ,u ,l ,yy ,_ ,_
byte eq ,eq ,eq ,eq ,eq ,eq ,eq
byte o ,n ,_ ,o ,e ,l ,n
byte 0 ; terminate text
text1
byte 0 ,i ,t ,e ,c ,a ,s
byte 0 ,ast,d ,m ,_ ,_ ,_
byte 0 ,eq ,eq ,eq ,eq ,eq ,eq
byte 0 ,i ,_ ,s ,a ,_ ,_
byte 0 ,o ,e ,b ,n ,h ,_
byte 0 ,_ ,t ,f ,_ ,_ ,m
byte 0 ,i ,i ,g ,t ,_ ,_
byte 0 ,s ,_ ,h ,_ ,e ,_
byte 0 ,xx ,_ ,o ,t ,n ,_
byte 0 ,_ ,t ,n ,t ,_ ,_
byte 0 ,v ,r ,_ ,o ,l ,ast
byte 0 ,s ,i ,_ ,s ,_ ,_
byte 0 ,t ,a ,l ,_ ,_ ,_
byte 0 ,eq ,eq ,eq ,eq ,eq ,eq
byte 0 ,e ,m ,r ,_ ,i ,e
;---------------------------------------------------------------------------
align 256
fonthi
eof
byte %00000000 ; value not used, address must be zero
_
byte %00000000
byte %00000000
byte %00000000
byte %00000000
byte %00000000
a
byte %10100000
byte %10100000
byte %11100000
byte %10100000
byte %01000000
b
byte %11000000
byte %10100000
byte %11000000
byte %10100000
byte %11000000
c
byte %01100000
byte %10000000
byte %10000000
byte %10000000
byte %01100000
d
byte %11000000
byte %10100000
byte %10100000
byte %10100000
byte %11000000
e
byte %11100000
byte %10000000
byte %11000000
byte %10000000
byte %11100000
f
byte %10000000
byte %10000000
byte %11000000
byte %10000000
byte %11100000
g
byte %01100000
byte %10100000
byte %10100000
byte %10000000
byte %01100000
h
byte %10100000
byte %10100000
byte %11100000
byte %10100000
byte %10100000
i
byte %01000000
byte %01000000
byte %01000000
byte %01000000
byte %01000000
j
byte %10000000
byte %01000000
byte %01000000
byte %01000000
byte %11100000
k
byte %10100000
byte %10100000
byte %11000000
byte %10100000
byte %10000000
l
byte %11100000
byte %10000000
byte %10000000
byte %10000000
byte %10000000
m
byte %10100000
byte %10100000
byte %10100000
byte %11100000
byte %10100000
n
byte %10100000
byte %10100000
byte %10100000
byte %10100000
byte %11000000
o
byte %01000000
byte %10100000
byte %10100000
byte %10100000
byte %01000000
p
byte %10000000
byte %10000000
byte %11000000
byte %10100000
byte %11000000
q
byte %01100000
byte %11100000
byte %10100000
byte %10100000
byte %01000000
r
byte %10100000
byte %10100000
byte %11000000
byte %10100000
byte %11000000
s
byte %11000000
byte %00100000
byte %01000000
byte %10000000
byte %01100000
t
byte %01000000
byte %01000000
byte %01000000
byte %01000000
byte %11100000
u
byte %01100000
byte %10100000
byte %10100000
byte %10100000
byte %10100000
v
byte %01000000
byte %01000000
byte %10100000
byte %10100000
byte %10100000
w
byte %10100000
byte %11100000
byte %10100000
byte %10100000
byte %10100000
xx
byte %10100000
byte %10100000
byte %01000000
byte %10100000
byte %10100000
yy
byte %01000000
byte %01000000
byte %01000000
byte %10100000
byte %10100000
z
byte %11100000
byte %10000000
byte %01000000
byte %00100000
byte %11100000
ast
byte %10100000
byte %01000000
byte %11100000
byte %01000000
byte %10100000
eq
byte %00000000
byte %11100000
byte %00000000
byte %11100000
byte %00000000
align 256
fontlo
;eof
byte %00000000
;_
byte %00000000
byte %00000000
byte %00000000
byte %00000000
byte %00000000
;a
byte %00001010
byte %00001010
byte %00001110
byte %00001010
byte %00000100
;b
byte %00001100
byte %00001010
byte %00001100
byte %00001010
byte %00001100
;c
byte %00000110
byte %00001000
byte %00001000
byte %00001000
byte %00000110
;d
byte %00001100
byte %00001010
byte %00001010
byte %00001010
byte %00001100
;e
byte %00001110
byte %00001000
byte %00001100
byte %00001000
byte %00001110
;f
byte %00001000
byte %00001000
byte %00001100
byte %00001000
byte %00001110
;g
byte %00000110
byte %00001010
byte %00001010
byte %00001000
byte %00000110
;h
byte %00001010
byte %00001010
byte %00001110
byte %00001010
byte %00001010
;i
byte %00000100
byte %00000100
byte %00000100
byte %00000100
byte %00000100
;j
byte %00001000
byte %00000100
byte %00000100
byte %00000100
byte %00001110
;k
byte %00001010
byte %00001010
byte %00001100
byte %00001010
byte %00001000
;l
byte %00001110
byte %00001000
byte %00001000
byte %00001000
byte %00001000
;m
byte %00001010
byte %00001010
byte %00001010
byte %00001110
byte %00001010
;n
byte %00001010
byte %00001010
byte %00001010
byte %00001010
byte %00001100
;o
byte %00000100
byte %00001010
byte %00001010
byte %00001010
byte %00000100
;p
byte %00001000
byte %00001000
byte %00001100
byte %00001010
byte %00001100
;q
byte %00000110
byte %00001110
byte %00001010
byte %00001010
byte %00000100
;r
byte %00001010
byte %00001010
byte %00001100
byte %00001010
byte %00001100
;s
byte %00001100
byte %00000010
byte %00000100
byte %00001000
byte %00000110
;t
byte %00000100
byte %00000100
byte %00000100
byte %00000100
byte %00001110
;u
byte %00000110
byte %00001010
byte %00001010
byte %00001010
byte %00001010
;v
byte %00000100
byte %00000100
byte %00001010
byte %00001010
byte %00001010
;w
byte %00001010
byte %00001110
byte %00001010
byte %00001010
byte %00001010
;xx
byte %00001010
byte %00001010
byte %00000100
byte %00001010
byte %00001010
;yy
byte %00000100
byte %00000100
byte %00000100
byte %00001010
byte %00001010
;z
byte %00001110
byte %00001000
byte %00000100
byte %00000010
byte %00001110
;ast
byte %00001010
byte %00000100
byte %00001110
byte %00000100
byte %00001010
;eq
byte %00000000
byte %00001110
byte %00000000
byte %00001110
byte %00000000
;---------------------------------------------------------------------------
; Program Startup
;---------------------------------------------------------------------------
org $FFFC
.word Start
.word Start
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