; Prog8 definitions for the Commodore-64 ; These are the utility subroutines. ; ; Written by Irmen de Jong (irmen@razorvine.net) - license: GNU GPL 3.0 ; ; indent format: TABS, size=8 %import c64lib ~ c64utils { const uword ESTACK_LO = $ce00 const uword ESTACK_HI = $cf00 ; ----- utility functions ---- asmsub init_system () -> clobbers(A,X,Y) -> () { ; ---- initializes the machine to a sane starting state ; This means that the BASIC, KERNAL and CHARGEN ROMs are banked in, ; the VIC, SID and CIA chips are reset, screen is cleared, and the default IRQ is set. ; Also a different color scheme is chosen to identify ourselves a little. ; Uppercase charset is activated, and all three registers set to 0, status flags cleared. %asm {{ sei cld lda #%00101111 sta $00 lda #%00100111 sta $01 jsr c64.IOINIT jsr c64.RESTOR jsr c64.CINT lda #6 sta c64.EXTCOL lda #7 sta c64.COLOR lda #0 sta c64.BGCOL0 tax tay clc clv cli rts }} } asmsub ubyte2decimal (ubyte value @ A) -> clobbers() -> (ubyte @ Y, ubyte @ X, ubyte @ A) { ; ---- A to decimal string in Y/X/A (100s in Y, 10s in X, 1s in A) %asm {{ ldy #$2f ldx #$3a sec - iny sbc #100 bcs - - dex adc #10 bmi - adc #$2f rts }} } asmsub byte2decimal (ubyte value @ A) -> clobbers() -> (ubyte @ Y, ubyte @ X, ubyte @ A) { ; ---- A (signed byte) to decimal string in Y/X/A (100s in Y, 10s in X, 1s in A) ; note: the '-' is not part of the conversion here if it's a negative number %asm {{ cmp #0 bpl + eor #255 clc adc #1 + jmp ubyte2decimal }} } asmsub ubyte2hex (ubyte value @ A) -> clobbers(X) -> (ubyte @ A, ubyte @ Y) { ; ---- A to hex string in AY (first hex char in A, second hex char in Y) %asm {{ pha and #$0f tax ldy hex_digits,x pla lsr a lsr a lsr a lsr a tax lda hex_digits,x rts hex_digits .text "0123456789abcdef" ; can probably be reused for other stuff as well }} } str word2hex_output = "1234" ; 0-terminated, to make printing easier asmsub uword2hex (uword value @ AY) -> clobbers(A,X,Y) -> () { ; ---- convert 16 bit uword in A/Y into 4-character hexadecimal string into memory 'word2hex_output' %asm {{ sta c64.SCRATCH_ZPREG tya jsr ubyte2hex stx word2hex_output sty word2hex_output+1 lda c64.SCRATCH_ZPREG jsr ubyte2hex sta word2hex_output+2 sty word2hex_output+3 rts }} } ubyte[3] word2bcd_bcdbuff = [0, 0, 0] asmsub uword2bcd (uword value @ AY) -> clobbers(A,X) -> () { ; Convert an 16 bit binary value to BCD ; ; This function converts a 16 bit binary value in A/Y into a 24 bit BCD. It ; works by transferring one bit a time from the source and adding it ; into a BCD value that is being doubled on each iteration. As all the ; arithmetic is being done in BCD the result is a binary to decimal ; conversion. %asm {{ sta c64.SCRATCH_ZPB1 sty c64.SCRATCH_ZPREG sei ; disable interrupts because of bcd math sed ; switch to decimal mode lda #0 ; ensure the result is clear sta word2bcd_bcdbuff+0 sta word2bcd_bcdbuff+1 sta word2bcd_bcdbuff+2 ldx #16 ; the number of source bits - asl c64.SCRATCH_ZPB1 ; shift out one bit rol c64.SCRATCH_ZPREG lda word2bcd_bcdbuff+0 ; and add into result adc word2bcd_bcdbuff+0 sta word2bcd_bcdbuff+0 lda word2bcd_bcdbuff+1 ; propagating any carry adc word2bcd_bcdbuff+1 sta word2bcd_bcdbuff+1 lda word2bcd_bcdbuff+2 ; ... thru whole result adc word2bcd_bcdbuff+2 sta word2bcd_bcdbuff+2 dex ; and repeat for next bit bne - cld ; back to binary cli ; enable interrupts again rts }} } ubyte[5] word2decimal_output = 0 asmsub uword2decimal (uword value @ AY) -> clobbers(A,X,Y) -> () { ; ---- convert 16 bit uword in A/Y into decimal string into memory 'word2decimal_output' %asm {{ jsr uword2bcd lda word2bcd_bcdbuff+2 clc adc #'0' sta word2decimal_output ldy #1 lda word2bcd_bcdbuff+1 jsr + lda word2bcd_bcdbuff+0 + pha lsr a lsr a lsr a lsr a clc adc #'0' sta word2decimal_output,y iny pla and #$0f adc #'0' sta word2decimal_output,y iny rts }} } ; @todo this is python code for a str-to-ubyte function that doesn't use the basic rom: ;def str2ubyte(s, slen): ; hundreds_map = { ; 0: 0, ; 1: 100, ; 2: 200 ; } ; digitvalue = 0 ; result = 0 ; if slen==0: ; return digitvalue ; digitvalue = ord(s[slen-1])-48 ; slen -= 1 ; if slen==0: ; return digitvalue ; result = digitvalue ; digitvalue = 10 * (ord(s[slen-1])-48) ; result += digitvalue ; slen -= 1 ; if slen==0: ; return result ; digitvalue = hundreds_map[ord(s[slen-1])-48] ; result += digitvalue ; return result asmsub c64flt_FREADSTR (ubyte length @ A) -> clobbers(A,X,Y) -> () = $b7b5 ; @todo needed for (slow) str conversion below asmsub c64flt_GETADR () -> clobbers(X) -> (ubyte @ Y, ubyte @ A) = $b7f7 ; @todo needed for (slow) str conversion below asmsub c64flt_FTOSWORDYA () -> clobbers(X) -> (ubyte @ Y, ubyte @ A) = $b1aa ; @todo needed for (slow) str conversion below asmsub str2uword(str string @ AY) -> clobbers() -> (uword @ AY) { %asm {{ ;-- convert string (address in A/Y) to uword number in A/Y ; @todo don't use the (slow) kernel floating point conversion sta $22 sty $23 jsr _strlen2233 tya stx c64.SCRATCH_ZPREGX jsr c64flt_FREADSTR ; string to fac1 jsr c64flt_GETADR ; fac1 to unsigned word in Y/A ldx c64.SCRATCH_ZPREGX sta c64.SCRATCH_ZPREG tya ldy c64.SCRATCH_ZPREG rts _strlen2233 ;-- return the length of the (zero-terminated) string at $22/$23, in Y ldy #0 - lda ($22),y beq + iny bne - + rts }} } asmsub str2word(str string @ AY) -> clobbers() -> (word @ AY) { %asm {{ ;-- convert string (address in A/Y) to signed word number in A/Y ; @todo don't use the (slow) kernel floating point conversion sta $22 sty $23 jsr str2uword._strlen2233 tya stx c64.SCRATCH_ZPREGX jsr c64flt_FREADSTR ; string to fac1 jsr c64flt_FTOSWORDYA ; fac1 to unsigned word in Y/A ldx c64.SCRATCH_ZPREGX sta c64.SCRATCH_ZPREG tya ldy c64.SCRATCH_ZPREG rts }} } asmsub str2ubyte(str string @ AY) -> clobbers(Y) -> (ubyte @ A) { %asm {{ ;-- convert string (address in A/Y) to ubyte number in A ; @todo don't use the (slow) kernel floating point conversion jmp str2uword }} } asmsub str2byte(str string @ AY) -> clobbers(Y) -> (byte @ A) { %asm {{ ;-- convert string (address in A/Y) to byte number in A ; @todo don't use the (slow) kernel floating point conversion jmp str2word }} } ; @todo string to 32 bit unsigned integer http://www.6502.org/source/strings/ascii-to-32bit.html %asm {{ ; copy memory UP from (SCRATCH_ZPWORD1) to (SCRATCH_ZPWORD2) of length X/Y (16-bit, X=lo, Y=hi) ; clobbers register A,X,Y memcopy16_up .proc source = SCRATCH_ZPWORD1 dest = SCRATCH_ZPWORD2 length = SCRATCH_ZPB1 ; (and SCRATCH_ZPREG) stx length sty length+1 ldx length ; move low byte of length into X bne + ; jump to start if X > 0 dec length ; subtract 1 from length + ldy #0 ; set Y to 0 - lda (source),y ; set A to whatever (source) points to offset by Y sta (dest),y ; move A to location pointed to by (dest) offset by Y iny ; increment Y bne + ; if Y<>0 then (rolled over) then still moving bytes inc source+1 ; increment hi byte of source inc dest+1 ; increment hi byte of dest + dex ; decrement X (lo byte counter) bne - ; if X<>0 then move another byte dec length ; weve moved 255 bytes, dec length bpl - ; if length is still positive go back and move more rts ; done .pend ; copy memory UP from (SCRATCH_ZPWORD1) to (AY) with length X (1 to 256, 0 meaning 256) ; destination must not overlap, or be before start, then overlap is possible. ; clobbers A, X, Y memcopy .proc sta c64.SCRATCH_ZPWORD2 sty c64.SCRATCH_ZPWORD2+1 ldy #0 - lda (c64.SCRATCH_ZPWORD1), y sta (c64.SCRATCH_ZPWORD2), y iny dex bne - rts .pend ; fill memory from (SCRATCH_ZPWORD1), length XY, with value in A. ; clobbers X, Y memset .proc stx SCRATCH_ZPB1 sty SCRATCH_ZPREG ldy #0 ldx SCRATCH_ZPREG beq _lastpage _fullpage sta (SCRATCH_ZPWORD1),y iny bne _fullpage inc SCRATCH_ZPWORD1+1 ; next page dex bne _fullpage _lastpage ldy SCRATCH_ZPB1 beq + - dey sta (SCRATCH_ZPWORD1),y bne - + rts .pend ; fill memory from (SCRATCH_ZPWORD1) number of words in SCRATCH_ZPWORD2, with word value in AY. ; clobbers A, X, Y memsetw .proc sta _mod1+1 ; self-modify sty _mod1b+1 ; self-modify sta _mod2+1 ; self-modify sty _mod2b+1 ; self-modify ldx SCRATCH_ZPWORD1 stx SCRATCH_ZPB1 ldx SCRATCH_ZPWORD1+1 inx stx SCRATCH_ZPREG ; second page ldy #0 ldx SCRATCH_ZPWORD2+1 beq _lastpage _fullpage _mod1 lda #0 ; self-modified sta (SCRATCH_ZPWORD1),y ; first page sta (SCRATCH_ZPB1),y ; second page iny _mod1b lda #0 ; self-modified sta (SCRATCH_ZPWORD1),y ; first page sta (SCRATCH_ZPB1),y ; second page iny bne _fullpage inc SCRATCH_ZPWORD1+1 ; next page pair inc SCRATCH_ZPWORD1+1 ; next page pair inc SCRATCH_ZPB1+1 ; next page pair inc SCRATCH_ZPB1+1 ; next page pair dex bne _fullpage _lastpage ldx SCRATCH_ZPWORD2 beq _done ldy #0 - _mod2 lda #0 ; self-modified sta (SCRATCH_ZPWORD1), y inc SCRATCH_ZPWORD1 bne _mod2b inc SCRATCH_ZPWORD1+1 _mod2b lda #0 ; self-modified sta (SCRATCH_ZPWORD1), y inc SCRATCH_ZPWORD1 bne + inc SCRATCH_ZPWORD1+1 + dex bne - _done rts .pend }} asmsub set_irqvec_excl() -> clobbers(A) -> () { %asm {{ sei lda #<_irq_handler sta c64.CINV lda #>_irq_handler sta c64.CINV+1 cli rts _irq_handler jsr irq.irq lda #$ff sta c64.VICIRQ ; acknowledge raster irq lda c64.CIA1ICR ; acknowledge CIA1 interrupt jmp c64.IRQDFEND ; end irq processing - don't call kernel }} } asmsub set_irqvec() -> clobbers(A) -> () { %asm {{ sei lda #<_irq_handler sta c64.CINV lda #>_irq_handler sta c64.CINV+1 cli rts _irq_handler jsr irq.irq jmp c64.IRQDFRT ; continue with normal kernel irq routine }} } asmsub restore_irqvec() -> clobbers() -> () { %asm {{ sei lda #c64.IRQDFRT sta c64.CINV+1 lda #0 sta c64.IREQMASK ; disable raster irq lda #%10000001 sta c64.CIA1ICR ; restore CIA1 irq cli rts }} } asmsub set_rasterirq(uword rasterpos @ AY) -> clobbers(A) -> () { %asm {{ sei jsr _setup_raster_irq lda #<_raster_irq_handler sta c64.CINV lda #>_raster_irq_handler sta c64.CINV+1 cli rts _raster_irq_handler jsr irq.irq lda #$ff sta c64.VICIRQ ; acknowledge raster irq jmp c64.IRQDFRT _setup_raster_irq pha lda #%01111111 sta c64.CIA1ICR ; "switch off" interrupts signals from cia-1 sta c64.CIA2ICR ; "switch off" interrupts signals from cia-2 and c64.SCROLY sta c64.SCROLY ; clear most significant bit of raster position lda c64.CIA1ICR ; ack previous irq lda c64.CIA2ICR ; ack previous irq pla sta c64.RASTER ; set the raster line number where interrupt should occur cpy #0 beq + lda c64.SCROLY ora #%10000000 sta c64.SCROLY ; set most significant bit of raster position + lda #%00000001 sta c64.IREQMASK ;enable raster interrupt signals from vic rts }} } asmsub set_rasterirq_excl(uword rasterpos @ AY) -> clobbers(A) -> () { %asm {{ sei jsr set_rasterirq._setup_raster_irq lda #<_raster_irq_handler sta c64.CINV lda #>_raster_irq_handler sta c64.CINV+1 cli rts _raster_irq_handler jsr irq.irq lda #$ff sta c64.VICIRQ ; acknowledge raster irq jmp c64.IRQDFEND ; end irq processing - don't call kernel }} } } ; ------ end of block c64utils ~ c64scr { ; ---- this block contains (character) Screen and text I/O related functions ---- asmsub clear_screen (ubyte char @ A, ubyte color @ Y) -> clobbers(A,X) -> () { ; ---- clear the character screen with the given fill character and character color. ; (assumes screen is at $0400, could be altered in the future with self-modifying code) ; @todo some byte var to set the SCREEN ADDR HI BYTE %asm {{ sta _loop + 1 ; self-modifying stx c64.SCRATCH_ZPB1 ldx #0 _loop lda #0 sta c64.Screen,x sta c64.Screen+$0100,x sta c64.Screen+$0200,x sta c64.Screen+$02e8,x tya sta c64.Colors,x sta c64.Colors+$0100,x sta c64.Colors+$0200,x sta c64.Colors+$02e8,x inx bne _loop lda _loop+1 ; restore A and X ldx c64.SCRATCH_ZPB1 rts }} } asmsub scroll_left_full (ubyte alsocolors @ Pc) -> clobbers(A, X, Y) -> () { ; ---- scroll the whole screen 1 character to the left ; contents of the rightmost column are unchanged, you should clear/refill this yourself ; Carry flag determines if screen color data must be scrolled too %asm {{ bcs + jmp _scroll_screen + ; scroll the color memory ldx #0 ldy #38 - .for row=0, row<=12, row+=1 lda c64.Colors + 40*row + 1,x sta c64.Colors + 40*row,x .next inx dey bpl - ldx #0 ldy #38 - .for row=13, row<=24, row+=1 lda c64.Colors + 40*row + 1,x sta c64.Colors + 40*row,x .next inx dey bpl - _scroll_screen ; scroll the screen memory ldx #0 ldy #38 - .for row=0, row<=12, row+=1 lda c64.Screen + 40*row + 1,x sta c64.Screen + 40*row,x .next inx dey bpl - ldx #0 ldy #38 - .for row=13, row<=24, row+=1 lda c64.Screen + 40*row + 1,x sta c64.Screen + 40*row,x .next inx dey bpl - rts }} } asmsub scroll_right_full (ubyte alsocolors @ Pc) -> clobbers(A,X) -> () { ; ---- scroll the whole screen 1 character to the right ; contents of the leftmost column are unchanged, you should clear/refill this yourself ; Carry flag determines if screen color data must be scrolled too %asm {{ bcs + jmp _scroll_screen + ; scroll the color memory ldx #38 - .for row=0, row<=12, row+=1 lda c64.Colors + 40*row + 0,x sta c64.Colors + 40*row + 1,x .next dex bpl - ldx #38 - .for row=13, row<=24, row+=1 lda c64.Colors + 40*row,x sta c64.Colors + 40*row + 1,x .next dex bpl - _scroll_screen ; scroll the screen memory ldx #38 - .for row=0, row<=12, row+=1 lda c64.Screen + 40*row + 0,x sta c64.Screen + 40*row + 1,x .next dex bpl - ldx #38 - .for row=13, row<=24, row+=1 lda c64.Screen + 40*row,x sta c64.Screen + 40*row + 1,x .next dex bpl - rts }} } asmsub scroll_up_full (ubyte alsocolors @ Pc) -> clobbers(A,X) -> () { ; ---- scroll the whole screen 1 character up ; contents of the bottom row are unchanged, you should refill/clear this yourself ; Carry flag determines if screen color data must be scrolled too %asm {{ bcs + jmp _scroll_screen + ; scroll the color memory ldx #39 - .for row=1, row<=11, row+=1 lda c64.Colors + 40*row,x sta c64.Colors + 40*(row-1),x .next dex bpl - ldx #39 - .for row=12, row<=24, row+=1 lda c64.Colors + 40*row,x sta c64.Colors + 40*(row-1),x .next dex bpl - _scroll_screen ; scroll the screen memory ldx #39 - .for row=1, row<=11, row+=1 lda c64.Screen + 40*row,x sta c64.Screen + 40*(row-1),x .next dex bpl - ldx #39 - .for row=12, row<=24, row+=1 lda c64.Screen + 40*row,x sta c64.Screen + 40*(row-1),x .next dex bpl - rts }} } asmsub scroll_down_full (ubyte alsocolors @ Pc) -> clobbers(A,X) -> () { ; ---- scroll the whole screen 1 character down ; contents of the top row are unchanged, you should refill/clear this yourself ; Carry flag determines if screen color data must be scrolled too %asm {{ bcs + jmp _scroll_screen + ; scroll the color memory ldx #39 - .for row=23, row>=12, row-=1 lda c64.Colors + 40*row,x sta c64.Colors + 40*(row+1),x .next dex bpl - ldx #39 - .for row=11, row>=0, row-=1 lda c64.Colors + 40*row,x sta c64.Colors + 40*(row+1),x .next dex bpl - _scroll_screen ; scroll the screen memory ldx #39 - .for row=23, row>=12, row-=1 lda c64.Screen + 40*row,x sta c64.Screen + 40*(row+1),x .next dex bpl - ldx #39 - .for row=11, row>=0, row-=1 lda c64.Screen + 40*row,x sta c64.Screen + 40*(row+1),x .next dex bpl - rts }} } asmsub print (str text @ AY) -> clobbers(A,Y) -> () { ; ---- print null terminated string from A/Y ; note: the compiler contains an optimization that will replace ; a call to this subroutine with a string argument of just one char, ; by just one call to c64.CHROUT of that single char. @todo do this %asm {{ sta c64.SCRATCH_ZPB1 sty c64.SCRATCH_ZPREG ldy #0 - lda (c64.SCRATCH_ZPB1),y beq + jsr c64.CHROUT iny bne - + rts }} } asmsub print_p (str_p text @ AY) -> clobbers(A,X) -> (ubyte @ Y) { ; ---- print pstring (length as first byte) from A/Y, returns str len in Y %asm {{ sta c64.SCRATCH_ZPB1 sty c64.SCRATCH_ZPREG ldy #0 lda (c64.SCRATCH_ZPB1),y beq + tax - iny lda (c64.SCRATCH_ZPB1),y jsr c64.CHROUT dex bne - + rts ; output string length is in Y }} } asmsub print_ub0 (ubyte value @ A) -> clobbers(A,X,Y) -> () { ; ---- print the ubyte in A in decimal form, with left padding 0s (3 positions total) %asm {{ jsr c64utils.ubyte2decimal pha tya jsr c64.CHROUT txa jsr c64.CHROUT pla jmp c64.CHROUT }} } asmsub print_ub (ubyte value @ A) -> clobbers(A,X,Y) -> () { ; ---- print the ubyte in A in decimal form, without left padding 0s %asm {{ jsr c64utils.ubyte2decimal _print_byte_digits pha cpy #'0' bne _print_hundreds cpx #'0' bne _print_tens pla jmp c64.CHROUT _print_hundreds tya jsr c64.CHROUT _print_tens txa jsr c64.CHROUT pla jmp c64.CHROUT }} } asmsub print_b (byte value @ A) -> clobbers(A,X,Y) -> () { ; ---- print the byte in A in decimal form, without left padding 0s %asm {{ pha cmp #0 bpl + lda #'-' jsr c64.CHROUT + pla jsr c64utils.byte2decimal jmp print_ub._print_byte_digits }} } asmsub print_ubhex (ubyte prefix @ Pc, ubyte value @ A) -> clobbers(A,X,Y) -> () { ; ---- print the ubyte in A in hex form (if Carry is set, a radix prefix '$' is printed as well) %asm {{ bcc + pha lda #'$' jsr c64.CHROUT pla + jsr c64utils.ubyte2hex jsr c64.CHROUT tya jmp c64.CHROUT }} } asmsub print_uwhex (ubyte prefix @ Pc, uword value @ AY) -> clobbers(A,X,Y) -> () { ; ---- print the uword in A/Y in hexadecimal form (4 digits) ; (if Carry is set, a radix prefix '$' is printed as well) %asm {{ pha tya jsr print_ubhex pla clc jmp print_ubhex }} } asmsub print_uw0 (uword value @ AY) -> clobbers(A,X,Y) -> () { ; ---- print the uword in A/Y in decimal form, with left padding 0s (5 positions total) ; @todo shorter in loop form? %asm {{ jsr c64utils.uword2decimal lda c64utils.word2decimal_output jsr c64.CHROUT lda c64utils.word2decimal_output+1 jsr c64.CHROUT lda c64utils.word2decimal_output+2 jsr c64.CHROUT lda c64utils.word2decimal_output+3 jsr c64.CHROUT lda c64utils.word2decimal_output+4 jmp c64.CHROUT }} } asmsub print_uw (uword value @ AY) -> clobbers(A,X,Y) -> () { ; ---- print the uword in A/Y in decimal form, without left padding 0s %asm {{ jsr c64utils.uword2decimal ldy #0 lda c64utils.word2decimal_output cmp #'0' bne _pr_decimal iny lda c64utils.word2decimal_output+1 cmp #'0' bne _pr_decimal iny lda c64utils.word2decimal_output+2 cmp #'0' bne _pr_decimal iny lda c64utils.word2decimal_output+3 cmp #'0' bne _pr_decimal iny _pr_decimal lda c64utils.word2decimal_output,y jsr c64.CHROUT iny cpy #5 bcc _pr_decimal rts }} } asmsub print_w (word value @ AY) -> clobbers(A,X,Y) -> () { ; ---- print the (signed) word in A/Y in decimal form, without left padding 0s %asm {{ cpy #0 bpl + pha lda #'-' jsr c64.CHROUT tya eor #255 tay pla eor #255 clc adc #1 bcc + iny + jmp print_uw }} } asmsub input_chars (uword buffer @ AY) -> clobbers(A, X) -> (ubyte @ Y) { ; ---- Input a string (max. 80 chars) from the keyboard. Returns length in Y. ; It assumes the keyboard is selected as I/O channel! %asm {{ sta c64.SCRATCH_ZPWORD1 sty c64.SCRATCH_ZPWORD1+1 ldy #0 ; char counter = 0 - jsr c64.CHRIN cmp #$0d ; return (ascii 13) pressed? beq + ; yes, end. sta (c64.SCRATCH_ZPWORD1),y ; else store char in buffer iny bne - + lda #0 sta (c64.SCRATCH_ZPWORD1),y ; finish string with 0 byte rts }} } asmsub setchr (ubyte col @Y, ubyte row @A) -> clobbers(A) -> () { ; ---- set the character in SCRATCH_ZPB1 on the screen matrix at the given position %asm {{ sty c64.SCRATCH_ZPREG asl a tay lda _screenrows+1,y sta _mod+2 lda _screenrows,y clc adc c64.SCRATCH_ZPREG sta _mod+1 bcc + inc _mod+2 + lda c64.SCRATCH_ZPB1 _mod sta $ffff ; modified rts _screenrows .word $0400 + range(0, 1000, 40) }} } asmsub setclr (ubyte col @Y, ubyte row @A) -> clobbers(A) -> () { ; ---- set the color in SCRATCH_ZPB1 on the screen matrix at the given position %asm {{ sty c64.SCRATCH_ZPREG asl a tay lda _colorrows+1,y sta _mod+2 lda _colorrows,y clc adc c64.SCRATCH_ZPREG sta _mod+1 bcc + inc _mod+2 + lda c64.SCRATCH_ZPB1 _mod sta $ffff ; modified rts _colorrows .word $d800 + range(0, 1000, 40) }} } sub setchrclr (ubyte column, ubyte row, ubyte char, ubyte color) { ; ---- set char+color at the given position on the screen %asm {{ lda setchrclr_row asl a tay lda setchr._screenrows+1,y sta _charmod+2 adc #$d4 sta _colormod+2 lda setchr._screenrows,y clc adc setchrclr_column sta _charmod+1 sta _colormod+1 bcc + inc _charmod+2 inc _colormod+2 + lda setchrclr_char _charmod sta $ffff ; modified lda setchrclr_color _colormod sta $ffff ; modified rts }} } asmsub PLOT (ubyte col @ Y, ubyte row @ A) -> clobbers(A) -> () { ; ---- safe wrapper around PLOT kernel routine, to save the X register. %asm {{ stx c64.SCRATCH_ZPREGX tax clc jsr c64.PLOT ldx c64.SCRATCH_ZPREGX rts }} } } ; ---- end block c64scr