Commodore Disk User Volume 4 #11

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Commodore BASIC | 2022-10-26 | 7KB | 427 lines

10 *=49152 11 ! 12 ! disable interupts,set up 13 ! interupt vector,enable raster 14 ! interupt,set up vic banks, 15 ! disable hardware timer a, 16 ! re-enable interupts. 17 ! 20 setint sei 30 lda #<intr 40 sta 788 50 lda #>intr 60 sta 789 70 lda 53274 80 ora #1 90 sta 53274 100 lda 53265 110 and #127 120 sta 53265 130 lda #252 140 sta 53266 150 lda 56578 160 ora #3 170 sta 56578 180 lda 56576 190 and #252 200 ora #2 210 sta 56576 220 lda 56334 230 and #254 240 sta 56334 250 cli 251 ! 252 ! set screen colours, 253 ! set start values to be 254 ! stored in map & map+1 255 ! (see window) 256 ! 260 lda #0 270 sta 53280 280 sta 53281 290 lda #<32768 300 sta map 310 lda #>32768 320 sta map+1 997 ! 998 rts 1000 ! 1001 ! check to see if a scroll 1002 ! is taking place.if not jump 1003 ! to 'noscroll' otherwise 1004 ! check to see which of the 8 1005 ! possible directions we are 1006 ! scrolling in and process. 1007 ! 1020 intr lda way 1030 beq noscroll 1040 cmp #1 1050 bne w1 1060 jsr ysub 1070 jmp noscroll 1080 w1 cmp #2 1090 bne w2 1100 jsr yadd 1110 jmp noscroll 1120 w2 cmp #3 1130 bne w3 1140 jsr xsub 1150 jmp noscroll 1160 w3 cmp #4 1170 bne w4 1179 jsr xadd 1180 jmp noscroll 1181 w4 cmp #5 1182 bne w5 1183 jsr xadd 1184 jsr ysub 1185 jmp noscroll 1186 w5 cmp #6 1187 bne w6 1188 jsr ysub 1189 jsr xsub 1190 jmp noscroll 1191 w6 cmp #7 1192 bne w7 1193 jsr yadd 1194 jsr xadd 1195 jmp noscroll 1196 w7 cmp #8 1197 bne noscroll 1198 jsr yadd 1199 jsr xsub 1200 ! 1210 ! set up location of raster 1211 ! split and re-vector the 1212 ! interupt to process the 1213 ! status line (non moving 1214 ! screen) routine. 1215 ! 1240 noscroll lda #<statline 1250 sta 788 1260 lda #>statline 1270 sta 789 1280 lda raster 1290 sta 53266 1300 jmp exint 1301 ! 1302 ! set 40 column screen, 1303 ! clear scroll registers to 1304 ! ensure this section of the 1305 ! screen is still,re-vector 1306 ! the interupt to process the 1307 ! routine dealing with the 1308 ! scrolling section of the 1309 ! screen,jsr to 'control' routine 1310 ! 1315 statline lda #8 1320 sta 53270 1330 lda #23 1340 sta 53265 1350 lda #54 1360 sta 53272 1370 lda #<gamearea 1380 sta 788 1390 lda #>gamearea 1400 sta 789 1405 lda #7 1406 sta 53280 1410 jsr control 1415 lda #0 1416 sta 53280 1420 lda #252 1430 sta 53266 1440 jmp exint 1441 ! 1442 ! set 38 column,24 row screen 1443 ! print up screen from 1444 ! map & map+1,set values of 1445 ! scroll registers. 1446 ! 1450 gamearea lda 53270 1455 and #0 1456 ora #16 1470 ora xscroll 1480 sta 53270 1490 lda 53265 1500 and #248 1510 ora yscroll 1520 sta 53265 1610 lda #36 1620 sta 53272 1625 lda #6 1626 sta 53280 1650 jsr window 1651 lda #0 1652 sta 53280 1654 jmp intr 1655 ! 1656 ! signal that interupt has been 1657 ! processed,restore registers 1658 ! and return from interupt. 1659 ! 1660 exint lda #1 1670 sta $d019 1690 pla 1700 tay 1710 pla 1720 tax 1730 pla 1740 rti 1741 ! 1742 ! hardware scroll screen 1 pixel 1743 ! to the right.if screen has 1744 ! moved more than 1 char. then 1745 ! subtract 1 from 16 bit value in 1746 ! map & map+1. 1747 ! 1750 xadd lda 53270 1760 ora #248 1770 clc 1780 adc xspeed 1790 and #7 1800 sta xscroll 1810 bcc exxadd 1820 sec 1830 lda map 1840 sbc #1 1850 sta map 1860 lda map+1 1870 sbc #0 1880 sta map+1 1960 exxadd rts 1961 ! 1962 ! hardware scroll screen 1 pixel 1963 ! to the left.if screen has 1964 ! moved more than 1 char. then 1965 ! add 1 to 16 bit value 1966 ! in map & map+1. 1967 ! 1970 xsub lda 53270 1980 and #7 1990 sec 2000 sbc xspeed 2010 and #7 2020 sta xscroll 2030 bcs exxsub 2040 clc 2050 lda map 2060 adc #1 2070 sta map 2080 lda map+1 2090 adc #0 2100 sta map+1 2180 exxsub rts 2181 ! 2182 ! hardware scroll the screen 2183 ! down 1 pixel. if screen has 2184 ! moved more than 1 char then 2185 ! subtract number of screens 2186 ! horizontally in map multiplyed 2187 ! by 40 from 16 bit value in 2188 ! map & map+1. 2189 ! eg:- 2190 ! if there are 6 screen across 2191 ! in map then subtract 240. 2192 ! 2199 yadd lda 53265 2200 ora #248 2210 clc 2220 adc yspeed 2230 and #7 2240 sta yscroll 2250 bcc exyadd 2260 sec 2270 lda map 2280 sbc #240 2290 sta map 2300 lda map+1 2310 sbc #0 2320 sta map+1 2400 exyadd rts 2401 ! 2402 ! as above but scroll up 1 pixel 2403 ! and add same value if 2404 ! necessary. 2405 ! 2410 ysub lda 53265 2420 and #7 2430 sec 2440 sbc yspeed 2450 and #7 2460 sta yscroll 2470 bcs exysub 2480 clc 2490 lda map 2500 adc #240 2510 sta map 2520 lda map+1 2530 adc #0 2540 sta map+1 2620 exysub rts 4000 ! 4001 ! (see diagram 1 ):- 4002 ! print up 1000 bytes to screen, 4003 ! ( screen is at 17408), 4004 ! starting at memory location 4005 ! pointed at by values in 4006 ! map & map+1. 4007 ! 4070 window lda #<18432 4080 sta 253 4090 lda #>18432 4100 sta 254 4120 lda map 4130 sta 251 4140 lda map+1 4150 sta 252 4160 ldx #18 4180 windloop1 ldy #0 4190 windloop2 lda (251),y 4200 sta (253),y 4210 iny 4215 cpy #40 4220 bne windloop2 4230 lda 251 4240 clc 4250 adc #240 4260 sta 251 4270 bcc windlp2 4290 inc 252 4300 windlp2 lda 253 4310 clc 4320 adc #40 4330 sta 253 4340 bcc excal 4360 inc 254 4370 excal dex 4376 bne windloop1 4390 rts 4400 ! 4410 ! variables as follows :- 4411 ! 4412 ! 1 - lo,hi address of screen 4413 ! (row 0,column 0) in overall map 4414 ! 2 - posistion of raster split 4415 ! 3 - speed of x scroll 4416 ! 4 - speed of y scroll 4417 ! 5 - value of x scroll register 4418 ! 6 - value of y scroll register 4419 ! 7 - joystick x value 4420 ! 8 - joystick y value 4421 ! 9 - direction of scroll (0-8) 4422 ! 6000 map byt <32768,>32768 6030 raster byt 189 6060 xspeed byt 1 6070 yspeed byt 1 6080 xscroll byt 0 6090 yscroll byt 0 6100 dx byt 0 6110 dy byt 0 6160 way byt 0 6161 ! 6162 ! the values in way indicate 6163 ! the follwing:- 6164 ! 6165 ! 0 = no scrolling 6166 ! 1 = scroll up 6167 ! 2 = scroll down 6168 ! 3 = scroll left 6169 ! 4 = scroll right 6170 ! 5 = scroll up & right 6171 ! 6 = scroll up & left 6172 ! 7 = scroll down & right 6173 ! 8 = scroll down & left 6174 ! 6179 ! 6180 ! joystick reading routine. 6181 ! see page 345 of programmers 6182 ! reference guide for full 6183 ! explanation. 6184 ! 7000 joyread lda 56320 7010 ldy #0 7020 ldx #0 7025 ! 7030 lsr a 7040 bcs joy0 7050 dey 7060 joy0 lsr a 7070 bcs joy1 7080 iny 7090 joy1 lsr a 7100 bcs joy2 7110 dex 7120 joy2 lsr a 7130 bcs joy3 7140 inx 7150 joy3 lsr a 7160 stx dx 7170 sty dy 7180 rts 7190 ! 7191 ! main control routine :- 7192 ! decide which direction to 7193 ! scroll. 7194 ! 8000 control jsr joyread 8010 ldx dx 8020 ldy dy 8021 txa 8022 bne vertical 8023 tya 8024 bne vertical 8025 sta way 8026 rts 8030 vertical cpx #0 8040 bne horizontal 8050 upc cpy #255 8060 bne downc 8070 lda #2 8080 sta way 8090 rts 8100 downc cpy #1 8110 bne xvert 8120 lda #1 8130 sta way 8140 xvert rts 8150 horizontal cpy #0 8160 bne dia(NULL)nal 8170 leftc cpx #255 8180 bne rightc 8190 lda #4 8200 sta way 8210 rts 8220 rightc cpx #1 8230 bne outcon 8240 lda #3 8250 sta way 8260 outcon rts 8270 dia(NULL)nal cpy #255 8280 bne diagdown 8290 cpx #1 8300 bne uplft 8310 uprght lda #8 8320 sta way 8330 rts 8340 uplft cpx #255 8350 bne outcon 8360 lda #7 8370 sta way 8380 rts 8390 diagdown cpy #1 8400 bne xdiag 8410 cpx #1 8420 bne dwnlft 8440 dwnrght lda #6 8450 sta way 8460 rts 8470 dwnlft cpx #255 8480 bne xdiag 8490 lda #5 8500 sta way 8510 xdiag rts 8520 ! 8530 end