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Shortenned the VIC-20's cputc() by 17 bytes.

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Changed to a modified table look-up method to convert PetSCII to screen-codes.
This commit is contained in:
Greg King 2020-10-13 07:55:20 -04:00
parent 4905329ff6
commit e72e44d14f
1 changed files with 41 additions and 40 deletions
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81
libsrc/vic20/cputc.s
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@ -1,5 +1,6 @@
; ;
; Ullrich von Bassewitz, 06.08.1998 ; 1998-08-06, Ullrich von Bassewitz
; 2020-10-09, Greg King
; ;
; void cputcxy (unsigned char x, unsigned char y, char c); ; void cputcxy (unsigned char x, unsigned char y, char c);
; void cputc (char c); ; void cputc (char c);
@ -39,69 +40,64 @@ _cputcxy:
jsr gotoxy ; Set cursor, drop x and y jsr gotoxy ; Set cursor, drop x and y
pla ; Restore C pla ; Restore C
; Plot a character - also used as internal function ; Plot a character -- also used as an internal function
_cputc: cmp #$0A ; CR? _cputc: cmp #$0D ; Is it CBM '\n'?
bne L1
lda #0
sta CURS_X
beq plot ; Recalculate pointers
L1: cmp #$0D ; LF?
beq newline ; Recalculate pointers beq newline ; Recalculate pointers
cmp #$0A ; Is it CBM '\r'?
beq cr
; Printable char of some sort ; Printable char. of some sort
; Convert it from PetSCII into a screen-code
cmp #' ' cmp #$FF ; BASIC token?
bcc cputdirect ; Other control char bne convert
lda #$DE ; Pi symbol
convert:
tay tay
bmi L10 lsr a ; Divide by 256/8
cmp #$60 lsr a
bcc L2 lsr a
and #$DF lsr a
bne cputdirect ; Branch always lsr a
L2: and #$3F tax ; .X = %00000xxx
tya
eor pet_to_screen,x
cputdirect: cputdirect:
jsr putchar ; Write the character to the screen jsr putchar ; Write the character to the screen
; Advance cursor position ; Advance the cursor position
advance: advance:
iny iny
cpy #XSIZE cpy #XSIZE
bne L3 bne L3
jsr newline ; new line jsr newline ; Wrap around
ldy #0 ; + cr
cr: ldy #$00 ; Do carriage-return
L3: sty CURS_X L3: sty CURS_X
rts rts
; Move down by one full screen-line. Note: this routine doesn't scroll.
;
; (Both screen RAM and color RAM are aligned to page boundaries.
; Therefore, the lower bytes of their addresses have the same values.
; Shorten the code by taking advantage of that fact.)
newline: newline:
clc clc
lda #XSIZE lda #XSIZE
adc SCREEN_PTR adc SCREEN_PTR
sta SCREEN_PTR sta SCREEN_PTR
bcc L4
inc SCREEN_PTR+1
clc
L4: lda #XSIZE
adc CRAM_PTR
sta CRAM_PTR sta CRAM_PTR
bcc L5 bcc L5
inc SCREEN_PTR+1
inc CRAM_PTR+1 inc CRAM_PTR+1
L5: inc CURS_Y L5: inc CURS_Y
rts rts
; Handle character if high bit set
L10: and #$7F
cmp #$7F ; PI?
bne L11
lda #$5E ; Load screen code for PI
L11: ora #$40
bne cputdirect
; Set cursor position, calculate RAM pointers ; Set cursor position, calculate RAM pointers
@ -111,14 +107,19 @@ plot: ldy CURS_X
jmp PLOT ; Set the new cursor jmp PLOT ; Set the new cursor
; Write one character to the screen without doing anything else,
; Write one character to the screen without doing anything else, return X ; return the X position in .Y
; position in Y
putchar: putchar:
ora RVS ; Set revers bit ora RVS ; Set revers bit
ldy CURS_X ldy CURS_X
sta (SCREEN_PTR),y ; Set char sta (SCREEN_PTR),y ; Set char.
lda CHARCOLOR lda CHARCOLOR
sta (CRAM_PTR),y ; Set color sta (CRAM_PTR),y ; Set color
rts rts
.rodata
pet_to_screen:
.byte %10000000,%00000000,%01000000,%00100000 ; PetSCII -> screen-code
.byte %01000000,%11000000,%10000000,%10000000