=========================================================================== ÓORRY THAT THIS IS LATER THAN É HAD HOPED TO GET IT OUT, BUT HERE IT IS -- ĹXPECT ANOTHER ONE SOON IN A MONTH OR TWO DEPENDING ON SUBMISSIONS... ĐRAISE, ĂOMMENTS, (ÉT SUCKS, É LOVED IT, ETC) ARE WELCOME -> DUCK@PEMBVAX1.PEMBROKE.EDU. ÍANY THANKS TO ĂRAIG ÂRUCE FOR HIS ARTICLE ON LINE DRAWING / DOT PLOTTING WITH THE 80 COLUMN SCREEN ON THE Ă=128. =============================================================================== ČACKING / ÔHIS ÍAGAZINE BY ĂRAIG ÔAYLOR DUCK@PEMBVAX1.PEMBROKE.EDU ÄEF: ČACKER - ÎOUN - Á TALENTED AMATEUR USER OF COMPUTERS. ÓOURCE - ×EBSTER'S ÎEW ×ORLD ÄICTIONARY ĂORRECTION: ČACKER - ÎOUN - Á TALENTED USER OF COMPUTERS. ÔHERE, NOW THAT WE GOT THAT OUT OF THE WAY, LET'S SEE HOW SOME PEOPLE INTERPRET THE WORD HACKER. ÉN THE 1980'S NEWSPAPERS, MAGAZINES, MOVIES - EVERYWHERE YA LOOKED PEOPLE WERE USING THE TERM "ČACKER" TO DENOTE A PERSON WHO MALICIOUSLY TRIED TO DESTROY / BORE ILL INTENT TOWARDS ANOTHER COMPUTER SYSTEM. ÔHIS WAS THE RESULT OF THE MISUNDERSTANDING OF THE ACTUAL DEFINITION OF "ČACKER" (UNDER MY CORRECTION ABOVE). ÔHIS MAGAZINE WILL NOT TELL PEOPLE HOW TO "PHREAK", HOW TO HHACK VOICE MAILBOXES AND OTHER ILLEGAL ACTIVITIES. ČOWEVER, IT WILL ATTEMPT TO REVEAL SOME OF THE "MYSTIQUE" BEHIND SOME OF THE NEW TECHNIQUES AND ABILITIES FOUND IN THE ĂOMMODORE 64 AND ĂOMMODORE 128 THAT ARE JUST NOW BEING REVEALED. ÉN THE EVENT THAT AN ARTICLE IS SUBMITTED AND THERE IS A QUESTION ABOUT IT'S ABILITY TO BE APPLIED TOWARDS ILLEGAL ACTIVITES, THE ARTICLE WILL BE CARRIED WITH A WARNING THAT THE INTENT IS NOT TOWARDS THAT ACTIVITY. ČOPEFULLY, THESE WILL NEVER COME ALONG. :-) ÔHE ĂOMMODORE 64 CAME OUT IN LATE 1982 (É BELIEVE) AND WAS KNOWN TO ONLY SUPPORT 16 COLORS, 320 X 200 RESOLUTION GRAPHICS OF 2 COLORS, 160X200 RESOLUTION GRAPHICS OF 4 COLORS. ÓINCE THEN PEOPLE HAVE PUSHED THE ĂOMMODORE 64 TO ITS LIMITS WITH APPARENT RESOLUTION OF 320 X 200 WITH A RESOLUTION OF 4 COLORS AND EVEN HIGHER... MORE THAN 8 SPRITES ON THE SCREEN... FAST HIGH-QUALITY DIGITIZED SOUNDS.... ÔHE ĂOMMODORE 128 CAME OUT AS AN "UPGRADE" FROM THE ĂOMMODORE 64 AND WITH IT'S UNIQUE MEMORY MANAGEMENT SCHEME AND THE Ú80A CHIP STILL ON THERE PEOPLE ARE STILL FINDING OUT UNIQUE AND INTERESTING WAYS TO EXPLORE THE Ă=128. ĎNE OF THE MOST INTERESTING HAS BEEN THAT OF THE SEPERATE VIDEO DISPLAY CHIP WHICH MAKES IT POSSIBLE TO DISPALY 640X200 RESOLUTION GRAPHICS QUICKLY AND EASILY. **ÁÔÔĹÎÔÉĎÎ** ÔHIS MAGAZINE IS GOING TO BE A SOURCEBOOK OF MANY PEOPLE - ÉF YOU KNOW ANYTHING ABOUT SOMETHING, PLEASE FEEL FREE TO SUBMIT IT. ĘUST MAIL THE ARTICLE TO THE FOLLOWING : DUCK@PEMBVAX1.PEMBROKE.EDU AND A SUBJECT OF "ÁŇÔÉĂĚĹ - " AND THEN THE ARTICLE NAME. ÔHE SOURCE CODE FOR ALL PROGRAMS MENTIONED WITHIN ARTICLES WILL BE PROVIDED AS WELL AS ANY EXECUTABLES UUENCODED SENT OUT SEPRATELY. [ĹD. ÎOTE - ÉN THIS ISSUE, THE SOURCE IS NOT SENT SEPERATELY DUE TO ONLY ONE ARTICLE WITH FILES] ÉN ADDITION, THE MAGAZINE WILL GO OUT WHEN THERE ARE ENOUGH ARTICLES COLLECTED. ÁLSO, É'M CURRENTLY IN COLLEGE - SO - IT WILL ALSO BE DEPENDANT ON FEW TESTS ETC BEING AROUND THE RELEASE PERIOD. ÉN THIS ISSUE: ÔITLE ÁUTHOR(S) ------------------------------------------------------------------------------ ČACKING - ÄEFINITION ĎF DUCK@PEMBVAX1.PEMBROKE.EDU ĚEARNING ÍĚ - ĐART 1 DUCK@PEMBVAX1.PEMBROKE.EDU 6502 ËNOWN/ŐNKNOWN ĎPCODES COMPILATION OF SEVERAL ÄOT ĐLOTTING & ÂITMAPPING F2RX@JUPITER.SUN.CSD.UNB.CA THE 8563 ÓCREEN. ** ÁLL ARTICLES AND FILES (Ă) 1992 BY THEIR RESPECTIVE AUTHORS. ============================================================================= ÂEGINNING ÍĚ - ĐART ĎNE (Ă) 1992 BY ĂRAIG ÔAYLOR ÔHE BEST WAY TO LEARN MACHINE LANGUAGE IS TO ACTUALLY CODE ROUTINES THAT YOU DON'T THINK WILL WORK, HOPE THAT THEY WORK, AND THEN FIGURE OUT WHY THEY DON'T WORK. (ÉF THEY DO WORK, YOU TRY TO FIGURE OUT WHY YOU DIDN'T THINK THEY'D WORK). ÉE: ÔČĹ ÂĹÓÔ ×ÁŮ ÔĎ ĚĹÁŇÎ ÁÎŮ ĐŇĎÇŇÁÍÍÉÎÇ ĚÁÎÇŐÁÇĹ ÉÓ ÔĎ ĐŇĎÇŇÁÍ ÉÎ ÔČÁÔ ĚÁÎÇŐÁÇĹ. ÁND ÍACHINE ĚANGUAGE IS A PROGRAMMING LANGUAGE. ÎOW, LET'S GET A FEW TERMS AND DEFINITIONS OUT OF THE WAY: ÍACHINE ĚANGUAGE - ÉNSTRUCTIONS THAT THE COMPUTER UNDERSTANDS AT A PRIMITIVE LEVEL AND EXECUTES ACCORDINGLY. ÁSSEMBLY ĚANGUAGE - ÉNSTRUCTIONS MORE UNDERSTANDABLE TO HUMANS THAN PURE ÍACHINE ĚANGUAGE THAT MAKES LIFE EASIER. ÁSSEMBLY: ÍACHINE: ĹXAMPLE: LDA #$00 $Á9 $00 ČUH? YOU MIGHT BE SAYING AT THE MOMENT. ÔURNS OUT THAT ĚÄÁ STANDS FOR, OR IS A MNEMONIC (COMPUTER PEOPLE ALWAYS COME UP WITH THESE BIG LONG WORDS -- YOU'LL SEE MNEMONIC'S OFTEN WHEN DEALING WITH MACHINE LANGUAGE) FOR THE FOLLOWING: "ĚĎÁÄ REGISTER Á WITH THE FOLLOWING VALUE" ^ ^ ^ ĂOOL 'EH? ŮEAH, BUT THERE'S SOMEBODY GRUMBLING NOW ABOUT WHY NOT MAKE IT ĚĎÁÄÁ ETC.. ČEY, THAT'S LIFE. (ÇŇÉÎ). ĎH, MORE DEFINITIONS: ŇEGISTER - Á LOCATION INSIDE THE ĂĐŐ THAT CAN BE MANIPULATED DIRECTLY WITHOUT HAVING TO ACCESS MEMORY. ÔHE "Á" REGISTER IS OFTEN CALLED THE ACCUMALATOR WHICH INDICATES ITS FUNCTION: ALL MATH AND LOGICAL MANIPULATIONS ARE DONE TO THE "Á" REGISTER (FROM HEREON OUT IT WILL BE REFERRED TO AS .Á). ÔHERE ARE TWO OTHER REGISTERS INSIDE THE 6502 PROCESSOR, SPECIFICALLY .Ř AND .Ů. ÔHESE REGISTERS HELP ACT AS COUNTERS AND INDEXES INTO MEMORY (SORTA LIKE MEM[X] IN PASCAL BUT NOT QUITE...). ÎOW, LET'S ADD 3 AND 5 AND LEAVE THE RESULT IN THE ACCUMALATOR (.Á). LDA #3 ; ČERE .Á = 3 (ANYTHING W/ A ; IS A ; COMMENT AND WILL BE IGNORED BY THE ASSEMBLER... CLC ; HU? - ÔHIS CLEARS THE CARRY. ÔHE 6502 ; DOES ADDITION *EVERYTIME* WITH THE CARRY ... SO IF WE CLEAR IT IT WON'T ; AFFECT THE RESULT. ADC #5 ; ÎOW, .Á = .Á + 5 AND WE'RE DONE. ÉF THE ĂĚĂ CONFUSED YOU THEN CONSIDER THAT IF YOU'RE ADDING A COLUMN OF #'S: 12 <--\__ÔHE 2 + 9 = 11, BUT WE PUT THE 1 DOWN AND SET THE CARRY TO 1. + 89 <---/ -- 101 ÔHEN WE SAY 1 + 8 + CARRY , WHICH IN THIS CASE HAPPENS TO = 1 AND WE GET 10 AND AGAIN WE SET THE CARRY AND WRITE DOWN 0. ÔHEN IT'S JUST THE CARRY AND WE WRITE THAT DOWN. ÉF WE DIDN'T CLEAR THE CARRY WE MAY HAVE ENDED UP WITH THE VALUE OF 9 INSTEAD 8 IF THE CARRY HAD HAPPENED TO BE SET. ÁAAGH, ÍATH - ĚET'S CONTINUE - ÔHE ĂĚĂ MNEMONIC STANDS FOR "ĂĚĹÁŇ ĂÁŇŇŮ" AND THE ÁÄĂ STANDS FOR "ÁÄÄ WITH ĂÁŇŇŮ". ĎN MANY PROCESSORS THERE IS A ÁÄÄ (WITHOUT A CARRY) BUT UNFORTUNATELY THE 6502 PROCESSOR INSIDE THE Ă=64 DOESN'T HAVE IT. ÓO WE'VE GOT: LOAD REG Á WITH THE VALUE 5 LDA #5 CLEAR THE CARRY CLC ADD REG A AND VALUE 3 ADC #3 ÉN ÂASIC IT'S JUST: Á = 5+3 ĎNE STATEMENT... ÉN ÍACHINE ĚANGUAGE YOU'VE GOT TO BREAK EVERYTHING DOWN INTO SMALLER AND SMALLER STEPS AND QUITE OFTEN THE ÍĚ LISTING WILL BE FAR LONGER THAN THE ÂÁÓÉĂ OR ĐÁÓĂÁĚ OR Ă EQUIVLENT. ÄEFINITIONS: ÁSSEMBLER - ĐROGRAM TAKES SOURCE CODE IN BASIC FORM OR FROM A FILE AND WRITES TO MEMORY OR A FILE THE RESULTING EXECUTABLE. ÁLLOWS HIGHER FLEXIBILITY THAN A MONITOR (SEE BELOW) DUE TO USE OF LABELS ETC AND NOT HAVING TO KEEP TRACK OF EACH ADDRESS WITHIN THE PROGRAM. ÍONITOR - Á PROGRAM, RESIDENT IN MEMORY, INVOKED BY A SYS CALL FROM BASIC OR BY HITTING THE RESTORE KEY THAT WILL LET YOU DISASSEMBLE, ASSEMBLE AND EXAMINE AREAS OF MEMORY AND EXECUTE PROGRAMS DIRECTLY FROM THE MONITOR. ŐSEFUL FOR DEBUGGING PROGRAMS AND FOR WRITING SHORT PROGRAMS. ĚET'S ENTER THE FOLLOWING INTO A MONITOR (IF YOU DON'T HAVE ONE THEN CONTACT DUCK@PEMBVAX1.PEMBROKE.EDU AND É'LL SEND YA ONE): 128: C64: >A 1300 LDA #$93 >A C000 LDA #$93 >A 1302 JSR $FFD2 >A C003 JSR $FFD2 >A 1305 RTS >A C005 RTS (EXIT MONITOR) (EXIT MONITOR) BANK15:SYS4864 SYS 49152 ×OW! ÉT CLEARED THE SCREEN. ÎEAT 'EH? ÂUT SEE HOW MUCH YA GOTTA BREAK PROBLEMS DOWN? ÔHE FIRST STATEMENT LOADS IN $93 HEX INTO THE ACCUMALATOR ($93 HEX JUST HAPPENS TO EQUAL 147 WHICH IS ALSO THE ĂOMMODORSCII CODE FOR CLEAR SCREEN. ĆOR A WHOLE LIST JUST LOOK IN THE BACK OF THE BOOK THAT CAME WITH THE COMPUTER). ÔHEN WE JUMP TO A SYSTEM ROUTINE WHICH ĂOMMODORE SO GRACIOUSLY SUPPLIED US WITH THAT PRINTS THE VALUE OF THE CHARACTER IN .Á TO THE SCREEN. (JSR $FFD2) THEN WE DO A ŇÔÓ (ŇEÔURN FROM ÓUBROUTINE) SO THAT WE WILL GO BACK TO BASIC AND THE ŇEADY PROMPT WHEN WE ARE FINISHED WITH THE SYS CALL. ŮOU Ă= 128 PEOPLE MAY BE WONDERING WHY YOU HAD TO DO A BANK 15 AND ASSEMBLE THE STUFF AT A DIFFERENT MEMORY LOCATION. ÔURNS OUT THAT THE Ă128 MEMORY MAP OF WHERE ROUTINES ETC ARE AT IS MUCH MORE COMPLEX THAN THE Ă=64 AND THUS YOU HAVE TO TELL BASIC WHICH BANK YOU WISH TO HAVE ALL SYS, PEEK, AND POKE CALLS TO TAKE PLACE IN. ÁLSO, $C000 AS USED ON THE Ă=64 IS NOT AN AREA THAT IS FREE TO USE ON THE Ă128 IN THIS MANNER. ÁSSIGNMENT: ÔAKE A LOOK @ THE DIFFERENT COMMANDS AS LISTED IN 6502 ĎPCODES AND TRY TO UNDERSTAND WHAT THEY DO. ĹXPERIMENT WITH THE JSR $FFD2 ROUTINE BY USING DIFFERENT VALUES ETC. ÎEXT ÔIME: ĐRINTING OUT STRINGS, AND UNDERSTANDING 'ÉNDEXING'. =========================================================================== 6502 ĎPCODES AND ŃUASI-ĎPCODES. ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ ÔHE FOLLOWING TABLE LISTS ALL OF THE AVAILABLE OPCODES ON THE 65XX LINE OF MICRO-PROCESSORS (SUCH AS THE 6510 ON THE Ă=64 AND THE 8502 ON THE Ă=128) ----------------------------------------------------------------------------- ÓTD ÍNEMONIC ČEX ÖALUE ÄESCRIPTION ÁDDRESSING ÍODE ÂYTES/ÔIME * ÂŇË $00 ÓTACK <- ĐĂ, ĐĂ <- ($FFFE) (ÉMMEDIATE) 1/7 * ĎŇÁ $01 Á <- (Á) Ö Í (ÉND,Ř) 6/2 ĘÁÍ $02 [LOCKS UP MACHINE] (ÉMPLIED) 1/- ÓĚĎ $03 Í <- (Í >> 1) + Á + Ă (ÉND,Ř) 2/8 ÎĎĐ $04 [NO OPERATION] (Ú-ĐAGE) 2/3 * ĎŇÁ $05 Á <- (Á) Ö Í (Ú-ĐAGE) 2/3 * ÁÓĚ $06 Ă <- Á7, Á <- (Á) << 1 (Ú-ĐAGE) 2/5 ÓĚĎ $07 Í <- (Í >> 1) + Á + Ă (Ú-ĐAGE) 2/5 * ĐČĐ $08 ÓTACK <- (Đ) (ÉMPLIED) 1/3 * ĎŇÁ $09 Á <- (Á) Ö Í (ÉMMEDIATE) 2/2 * ÁÓĚ $0Á Ă <- Á7, Á <- (Á) << 1 (ÁCCUMALATOR) 1/2 ÁÎĂ $0Â Á <- Á /\ Í, Ă=~Á7 (ÉMMEDIATE) 1/2 ÎĎĐ $0Ă [NO OPERATION] (ÁBSOLUTE) 3/4 * ĎŇÁ $0Ä Á <- (Á) Ö Í (ÁBSOLUTE) 3/4 * ÁÓĚ $0Ĺ Ă <- Á7, Á <- (Á) << 1 (ÁBSOLUTE) 3/6 ÓĚĎ $0Ć Í <- (Í >> 1) + Á + Ă (ÁBSOLUTE) 3/6 * ÂĐĚ $10 IF Î=0, ĐĂ = ĐĂ + OFFSET (ŇELATIVE) 2/2'2 * ĎŇÁ $11 Á <- (Á) Ö Í ((ÉND),Ů) 2/5'1 ĘÁÍ $12 [LOCKS UP MACHINE] (ÉMPLIED) 1/- ÓĚĎ $13 Í <- (Í >. 1) + Á + Ă ((ÉND),Ů) 2/8'5 ÎĎĐ $14 [NO OPERATION] (Ú-ĐAGE,Ř) 2/4 * ĎŇÁ $15 Á <- (Á) Ö Í (Ú-ĐAGE,Ř) 2/4 * ÁÓĚ $16 Ă <- Á7, Á <- (Á) << 1 (Ú-ĐAGE,Ř) 2/6 ÓĚĎ $17 Í <- (Í >> 1) + Á + Ă (Ú-ĐAGE,Ř) 2/6 * ĂĚĂ $18 Ă <- 0 (ÉMPLIED) 1/2 * ĎŇÁ $19 Á <- (Á) Ö Í (ÁBSOLUTE,Ů) 3/4'1 ÎĎĐ $1Á [NO OPERATION] (ÉMPLIED) 1/2 ÓĚĎ $1Â Í <- (Í >> 1) + Á + Ă (ÁBSOLUTE,Ů) 3/7 ÎĎĐ $1Ă [NO OPERATION] (ÁBSOLUTE,Ř) 2/4'1 * ĎŇÁ $1Ä Á <- (Á) Ö Í (ÁBSOLUTE,Ř) 3/4'1 * ÁÓĚ $1Ĺ Ă <- Á7, Á <- (Á) << 1 (ÁBSOLUTE,Ř) 3/7 ÓĚĎ $1Ć Í <- (Í >> 1) + Á + Ă (ÁBSOLUTE,Ř) 3/7 * ĘÓŇ $20 ÓTACK <- ĐĂ, ĐĂ <- ÁDDRESS (ÁBSOLUTE) 3/6 * ÁÎÄ $21 Á <- (Á) /\ Í (ÉND,Ř) 2/6 ĘÁÍ $22 [LOCKS UP MACHINE] (ÉMPLIED) 1/- ŇĚÁ $23 Í <- (Í << 1) /\ (Á) (ÉND,Ř) 2/8 * ÂÉÔ $24 Ú <- ~(Á /\ Í) Î<-Í7 Ö<-Í6 (Ú-ĐAGE) 2/3 * ÁÎÄ $25 Á <- (Á) /\ Í (Ú-ĐAGE) 2/3 * ŇĎĚ $26 Ă <- Á7 & Á <- Á << 1 + Ă (Ú-ĐAGE) 2/5 ŇĚÁ $27 Í <- (Í << 1) /\ (Á) (Ú-ĐAGE) 2/5'5 * ĐĚĐ $28 Á <- (ÓTACK) (ÉMPLIED) 1/4 * ÁÎÄ $29 Á <- (Á) /\ Í (ÉMMEDIATE) 2/2 * ŇĎĚ $2Á Ă <- Á7 & Á <- Á << 1 + Ă (ÁCCUMALATOR) 1/2 ÁÎĂ $2Â Á <- Á /\ Í, Ă <- ~Á7 (ÉMMEDIATE9 1/2 * ÂÉÔ $2Ă Ú <- ~(Á /\ Í) Î<-Í7 Ö<-Í6 (ÁBSOLUTE) 3/4 * ÁÎÄ $2Ä Á <- (Á) /\ Í (ÁBSOLUTE) 3/4 * ŇĎĚ $2Ĺ Ă <- Á7 & Á <- Á << 1 + Ă (ÁBSOLUTE) 3/6 ŇĚÁ $2Ć Í <- (Í << 1) /\ (Á) (ÁBSOLUTE) 3/6'5 * ÂÍÉ $30 IF Î=1, ĐĂ = ĐĂ + OFFSET (ŇELATIVE) 2/2'2 * ÁÎÄ $31 Á <- (Á) /\ Í ((ÉND),Ů) 2/5'1 ĘÁÍ $32 [LOCKS UP MACHINE] (ÉMPLIED) 1/- ŇĚÁ $33 Í <- (Í << 1) /\ (Á) ((ÉND),Ů) 2/8'5 ÎĎĐ $34 [NO OPERATION] (Ú-ĐAGE,Ř) 2/4 * ÁÎÄ $35 Á <- (Á) /\ Í (Ú-ĐAGE,Ř) 2/4 * ŇĎĚ $36 Ă <- Á7 & Á <- Á << 1 + Ă (Ú-ĐAGE,Ř) 2/6 ŇĚÁ $37 Í <- (Í << 1) /\ (Á) (Ú-ĐAGE,Ř) 2/6'5 * ÓĹĂ $38 Ă <- 1 (ÉMPLIED) 1/2 * ÁÎÄ $39 Á <- (Á) /\ Í (ÁBSOLUTE,Ů) 3/4'1 ÎĎĐ $3Á [NO OPERATION] (ÉMPLIED) 1/2 ŇĚÁ $3Â Í <- (Í << 1) /\ (Á) (ÁBSOLUTE,Ů) 3/7'5 ÎĎĐ $3Ă [NO OPERATION] (ÁBSOLUTE,Ř) 3/4'1 * ÁÎÄ $3Ä Á <- (Á) /\ Í (ÁBSOLUTE,Ř) 3/4'1 * ŇĎĚ $3Ĺ Ă <- Á7 & Á <- Á << 1 + Ă (ÁBSOLUTE,Ř) 3/7 ŇĚÁ $3Ć Í <- (Í << 1) /\ (Á) (ÁBSOLUTE,Ř) 3/7'5 * ŇÔÉ $40 Đ <- (ÓTACK), ĐĂ <-(ÓTACK) (ÉMPLIED) 1/6 * ĹĎŇ $41 Á <- (Á) \-/ Í (ÉND,Ř) 2/6 ĘÁÍ $42 [LOCKS UP MACHINE] (ÉMPLIED) 1/- ÓŇĹ $43 Í <- (Í >> 1) \-/ Á (ÉND,Ř) 2/8 ÎĎĐ $44 [NO OPERATION] (Ú-ĐAGE) 2/3 * ĹĎŇ $45 Á <- (Á) \-/ Í (Ú-ĐAGE) 2/3 * ĚÓŇ $46 Ă <- Á0, Á <- (Á) >> 1 (ÁBSOLUTE,Ř) 3/7 ÓŇĹ $47 Í <- (Í >> 1) \-/ Á (Ú-ĐAGE) 2/5 * ĐČÁ $48 ÓTACK <- (Á) (ÉMPLIED) 1/3 * ĹĎŇ $49 Á <- (Á) \-/ Í (ÉMMEDIATE) 2/2 * ĚÓŇ $4Á Ă <- Á0, Á <- (Á) >> 1 (ÁCCUMALATOR) 1/2 ÁÓŇ $4Â Á <- [(Á /\ Í) >> 1] (ÉMMEDIATE) 1/2 * ĘÍĐ $4Ă ĐĂ <- ÁDDRESS (ÁBSOLUTE) 3/3 * ĹĎŇ $4Ä Á <- (Á) \-/ Í (ÁBSOLUTE) 3/4 * ĚÓŇ $4Ĺ Ă <- Á0, Á <- (Á) >> 1 (ÁBSOLUTE) 3/6 ÓŇĹ $4Ć Í <- (Í >> 1) \-/ Á (ÁBSOLUTE) 3/6 * ÂÖĂ $50 IF Ö=0, ĐĂ = ĐĂ + OFFSET (ŇELATIVE) 2/2'2 * ĹĎŇ $51 Á <- (Á) \-/ Í ((ÉND),Ů) 2/5'1 ĘÁÍ $52 [LOCKS UP MACHINE] (ÉMPLIED) 1/- ÓŇĹ $53 Í <- (Í >> 1) \-/ Á ((ÉND),Ů) 2/8 ÎĎĐ $54 [NO OPERATION] (Ú-ĐAGE,Ř) 2/4 * ĹĎŇ $55 Á <- (Á) \-/ Í (Ú-ĐAGE,Ř) 2/4 * ĚÓŇ $56 Ă <- Á0, Á <- (Á) >> 1 (Ú-ĐAGE,Ř) 2/6 ÓŇĹ $57 Í <- (Í >> 1) \-/ Á (Ú-ĐAGE,Ř) 2/6 * ĂĚÉ $58 É <- 0 (ÉMPLIED) 1/2 * ĹĎŇ $59 Á <- (Á) \-/ Í (ÁBSOLUTE,Ů) 3/4'1 ÎĎĐ $5Á [NO OPERATION] (ÉMPLIED) 1/2 ÓŇĹ $5Â Í <- (Í >> 1) \-/ Á (ÁBSOLUTE,Ů) 3/7 ÎĎĐ $5Ă [NO OPERATION] (ÁBSOLUTE,Ř) 3/4'1 * ĹĎŇ $5Ä Á <- (Á) \-/ Í (ÁBSOLUTE,Ř) 3/4'1 ÓŇĹ $5Ć Í <- (Í >> 1) \-/ Á (ÁBSOLUTE,Ř) 3/7 * ŇÔÓ $60 ĐĂ <- (ÓTACK) (ÉMPLIED) 1/6 * ÁÄĂ $61 Á <- (Á) + Í + Ă (ÉND,Ř) 2/6 ĘÁÍ $62 [LOCKS UP MACHINE] (ÉMPLIED) 1/- ŇŇÁ $63 Í <- (Í >> 1) + (Á) + Ă (ÉND,Ř) 2/8'5 ÎĎĐ $64 [NO OPERATION] (Ú-ĐAGE) 2/3 * ÁÄĂ $65 Á <- (Á) + Í + Ă (Ú-ĐAGE) 2/3 * ŇĎŇ $66 Ă<-Á0 & Á<- (Á7=Ă + Á>>1) (Ú-ĐAGE) 2/5 ŇŇÁ $67 Í <- (Í >> 1) + (Á) + Ă (Ú-ĐAGE) 2/5'5 * ĐĚÁ $68 Á <- (ÓTACK) (ÉMPLIED) 1/4 * ÁÄĂ $69 Á <- (Á) + Í + Ă (ÉMMEDIATE) 2/2 * ŇĎŇ $6Á Ă<-Á0 & Á<- (Á7=Ă + Á>>1) (ÁCCUMALATOR) 1/2 ÁŇŇ $6Â Á <- [(Á /\ Í) >> 1] (ÉMMEDIATE) 1/2'5 * ĘÍĐ $6Ă ĐĂ <- ÁDDRESS (ÉNDIRECT) 3/5 * ÁÄĂ $6Ä Á <- (Á) + Í + Ă (ÁBSOLUTE) 3/4 * ŇĎŇ $6Ĺ Ă<-Á0 & Á<- (Á7=Ă + Á>>1) (ÁBSOLUTE) 3/6 ŇŇÁ $6Ć Í <- (Í >> 1) + (Á) + Ă (ÁBSOLUTE) 3/6'5 * ÂÖÓ $70 IF Ö=1, ĐĂ = ĐĂ + OFFSET (ŇELATIVE) 2/2'2 * ÁÄĂ $71 Á <- (Á) + Í + Ă ((ÉND),Ů) 2/5'1 ĘÁÍ $72 [LOCKS UP MACHINE] (ÉMPLIED) 1/- ŇŇÁ $73 Í <- (Í >> 1) + (Á) + Ă ((ÉND),Ů) 2/8'5 ÎĎĐ $74 [NO OPERATION] (Ú-ĐAGE,Ř) 2/4 * ÁÄĂ $75 Á <- (Á) + Í + Ă (Ú-ĐAGE,Ř) 2/4 * ŇĎŇ $76 Ă<-Á0 & Á<- (Á7=Ă + Á>>1) (Ú-ĐAGE,Ř) 2/6 ŇŇÁ $77 Í <- (Í >> 1) + (Á) + Ă (Ú-ĐAGE,Ř) 2/6'5 * ÓĹÉ $78 É <- 1 (ÉMPLIED) 1/2 * ÁÄĂ $79 Á <- (Á) + Í + Ă (ÁBSOLUTE,Ů) 3/4'1 ÎĎĐ $7Á [NO OPERATION] (ÉMPLIED) 1/2 ŇŇÁ $7Â Í <- (Í >> 1) + (Á) + Ă (ÁBSOLUTE,Ů) 3/7'5 ÎĎĐ $7Ă [NO OPERATION] (ÁBSOLUTE,Ř) 3/4'1 * ÁÄĂ $7Ä Á <- (Á) + Í + Ă (ÁBSOLUTE,Ř) 3/4'1 * ŇĎŇ $7Ĺ Ă<-Á0 & Á<- (Á7=Ă + Á>>1) (ÁBSOLUTE,Ř) 3/7 ŇŇÁ $7Ć Í <- (Í >> 1) + (Á) + Ă (ÁBSOLUTE,Ř) 3/7'5 ÎĎĐ $80 [NO OPERATION] (ÉMMEDIATE) 2/2 * ÓÔÁ $81 Í <- (Á) (ÉND,Ř) 2/6 ÎĎĐ $82 [NO OPERATION] (ÉMMEDIATE) 2/2 ÓÁŘ $83 Í <- (Á) /\ (Ř) (ÉND,Ř) 2/6 * ÓÔŮ $84 Í <- (Ů) (Ú-ĐAGE) 2/3 * ÓÔÁ $85 Í <- (Á) (Ú-ĐAGE) 2/3 * ÓÔŘ $86 Í <- (Ř) (Ú-ĐAGE) 2/3 ÓÁŘ $87 Í <- (Á) /\ (Ř) (Ú-ĐAGE) 2/3 * ÄĹŮ $88 Ů <- (Ů) - 1 (ÉMPLIED) 1/2 ÎĎĐ $89 [NO OPERATION] (ÉMMEDIATE) 2/2 * ÔŘÁ $8Á Á <- (Ř) (ÉMPLIED) 1/2 ÁÎĹ $8Â Í <-[(Á)\/$ĹĹ] /\ (Ř)/\(Í) (ÉMMEDIATE) 2/2^4 * ÓÔŮ $8Ă Í <- (Ů) (ÁBSOLUTE) 3/4 * ÓÔÁ $8Ä Í <- (Á) (ÁBSOLUTE) 3/4 * ÓÔŘ $8Ĺ Í <- (Ř) (ÁBSOLUTE) 3/4 ÓÁŘ $8Ć Í <- (Á) /\ (Ř) (ÁBSOLUTE) 3/4 * ÂĂĂ $90 IF Ă=0, ĐĂ = ĐĂ + OFFSET (ŇELATIVE) 2/2'2 * ÓÔÁ $91 Í <- (Á) ((ÉND),Ů) 2/6 ĘÁÍ $92 [LOCKS UP MACHINE] (ÉMPLIED) 1/- ÓČÁ $93 Í <- (Á) /\ (Ř) /\ (ĐĂČ+1) (ÁBSOLUTE,Ř) 3/6'3 * ÓÔŮ $94 Í <- (Ů) (Ú-ĐAGE,Ř) 2/4 * ÓÔÁ $95 Í <- (Á) (Ú-ĐAGE,Ř) 2/4 ÓÁŘ $97 Í <- (Á) /\ (Ř) (Ú-ĐAGE,Ů) 2/4 * ÓÔŘ $96 Í <- (Ř) (Ú-ĐAGE,Ů) 2/4 * ÔŮÁ $98 Á <- (Ů) (ÉMPLIED) 1/2 * ÓÔÁ $99 Í <- (Á) (ÁBSOLUTE,Ů) 3/5 * ÔŘÓ $9Á Ó <- (Ř) (ÉMPLIED) 1/2 ÓČÓ $9Â Ř <- (Á) /\ (Ř), Ó <- (Ř) (ÁBSOLUTE,Ů) 3/5 Í <- (Ř) /\ (ĐĂČ+1) ÓČŮ $9Ă Í <- (Ů) /\ (ĐĂČ+1) (ÁBSOLUTE,Ů) 3/5'3 * ÓÔÁ $9Ä Í <- (Á) (ÁBSOLUTE,Ř) 3/5 ÓČŘ $9Ĺ Í <- (Ř) /\ (ĐĂČ+1) (ÁBSOLUTE,Ř) 3/5'3 ÓČÁ $9Ć Í <- (Á) /\ (Ř) /\ (ĐĂČ+1) (ÁBSOLUTE,Ů) 3/5'3 * ĚÄŮ $Á0 Ů <- Í (ÉMMEDIATE) 2/2 * ĚÄÁ $Á1 Á <- Í (ÉND,Ř) 2/6 * ĚÄŘ $Á2 Ř <- Í (ÉMMEDIATE) 2/2 ĚÁŘ $Á3 Á <- Í, Ř <- Í (ÉND,Ř) 2/6 * ĚÄŮ $Á4 Ů <- Í (Ú-ĐAGE) 2/3 * ĚÄÁ $Á5 Á <- Í (Ú-ĐAGE) 2/3 * ĚÄŘ $Á6 Ř <- Í (Ú-ĐAGE) 2/3 ĚÁŘ $Á7 Á <- Í, Ř <- Í (Ú-ĐAGE) 2/3 * ÔÁŮ $Á8 Ů <- (Á) (ÉMPLIED) 1/2 * ĚÄÁ $Á9 Á <- Í (ÉMMEDIATE) 2/2 * ÔÁŘ $ÁÁ Ř <- (Á) (ÉMPLIED) 1/2 ĚŘÁ $ÁÂ Ř04 <- (Ř04) /\ Í04 (ÉMMEDIATE) 1/2 Á04 <- (Á04) /\ Í04 * ĚÄŮ $ÁĂ Ů <- Í (ÁBSOLUTE) 3/4 * ĚÄÁ $ÁÄ Á <- Í (ÁBSOLUTE) 3/4 * ĚÄŘ $ÁĹ Ř <- Í (ÁBSOLUTE) 3/4 ĚÁŘ $ÁĆ Á <- Í, Ř <- Í (ÁBSOLUTE) 3/4 * ÂĂÓ $Â0 IF Ă=1, ĐĂ = ĐĂ + OFFSET (ŇELATIVE) 2/2'2 * ĚÄÁ $Â1 Á <- Í ((ÉND),Ů) 2/5'1 ĘÁÍ $Â2 [LOCKS UP MACHINE] (ÉMPLIED) 1/- ĚÁŘ $Â3 Á <- Í, Ř <- Í ((ÉND),Ů) 2/5'1 * ĚÄŮ $Â4 Ů <- Í (Ú-ĐAGE,Ř) 2/4 * ĚÄÁ $Â5 Á <- Í (Ú-ĐAGE,Ř) 2/4 * ĚÄŘ $Â6 Ř <- Í (Ú-ĐAGE,Ů) 2/4 ĚÁŘ $Â7 Á <- Í, Ř <- Í (Ú-ĐAGE,Ů) 2/4 * ĂĚÖ $Â8 Ö <- 0 (ÉMPLIED) 1/2 * ĚÄÁ $Â9 Á <- Í (ÁBSOLUTE,Ů) 3/4'1 * ÔÓŘ $ÂÁ Ř <- (Ó) (ÉMPLIED) 1/2 ĚÁĹ $ÂÂ Ř,Ó,Á <- (Ó /\ Í) (ÁBSOLUTE,Ů) 3/4'1 * ĚÄŮ $ÂĂ Ů <- Í (ÁBSOLUTE,Ř) 3/4'1 * ĚÄÁ $ÂÄ Á <- Í (ÁBSOLUTE,Ř) 3/4'1 * ĚÄŘ $ÂĹ Ř <- Í (ÁBSOLUTE,Ů) 3/4'1 ĚÁŘ $ÂĆ Á <- Í, Ř <- Í (ÁBSOLUTE,Ů) 3/4'1 * ĂĐŮ $Ă0 (Ů - Í) -> ÎÚĂ (ÉMMEDIATE) 2/2 * ĂÍĐ $Ă1 (Á - Í) -> ÎÚĂ (ÉND,Ř) 2/6 ÎĎĐ $Ă2 [NO OPERATION] (ÉMMEDIATE) 2/2 ÄĂĐ $Ă3 Í <- (Í)-1, (Á-Í) -> ÎÚĂ (ÉND,Ř) 2/8 * ĂĐŮ $Ă4 (Ů - Í) -> ÎÚĂ (Ú-ĐAGE) 2/3 * ĂÍĐ $Ă5 (Á - Í) -> ÎÚĂ (Ú-ĐAGE) 2/3 * ÄĹĂ $Ă6 Í <- (Í) - 1 (Ú-ĐAGE) 2/5 ÄĂĐ $Ă7 Í <- (Í)-1, (Á-Í) -> ÎÚĂ (Ú-ĐAGE) 2/5 * ÉÎŮ $Ă8 Ů <- (Ů) + 1 (ÉMPLIED) 1/2 * ĂÍĐ $Ă9 (Á - Í) -> ÎÚĂ (ÉMMEDIATE) 2/2 * ÄĹŘ $ĂÁ Ř <- (Ř) - 1 (ÉMPLIED) 1/2 ÓÂŘ $ĂÂ Ř <- (Ř)/\(Á) - Í (ÉMMEDIATE) 2/2 * ĂĐŮ $ĂĂ (Ů - Í) -> ÎÚĂ (ÁBSOLUTE) 3/4 * ĂÍĐ $ĂÄ (Á - Í) -> ÎÚĂ (ÁBSOLUTE) 3/4 * ÄĹĂ $ĂĹ Í <- (Í) - 1 (ÁBSOLUTE) 3/6 ÄĂĐ $ĂĆ Í <- (Í)-1, (Á-Í) -> ÎÚĂ (ÁBSOLUTE) 3/6 * ÂÎĹ $Ä0 IF Ú=0, ĐĂ = ĐĂ + OFFSET (ŇELATIVE) 2/2'2 * ĂÍĐ $Ä1 (Á - Í) -> ÎÚĂ ((ÉND),Ů) 2/5'1 ĘÁÍ $Ä2 [LOCKS UP MACHINE] (ÉMPLIED) 1/- ÄĂĐ $Ä3 Í <- (Í)-1, (Á-Í) -> ÎÚĂ ((ÉND),Ů) 2/8 ÎĎĐ $Ä4 [NO OPERATION] (Ú-ĐAGE,Ř) 2/4 * ĂÍĐ $Ä5 (Á - Í) -> ÎÚĂ (Ú-ĐAGE,Ř) 2/4 * ÄĹĂ $Ä6 Í <- (Í) - 1 (Ú-ĐAGE,Ř) 2/6 ÄĂĐ $Ä7 Í <- (Í)-1, (Á-Í) -> ÎÚĂ (Ú-ĐAGE,Ř) 2/6 * ĂĚÄ $Ä8 Ä <- 0 (ÉMPLIED) 1/2 * ĂÍĐ $Ä9 (Á - Í) -> ÎÚĂ (ÁBSOLUTE,Ů) 3/4'1 ÎĎĐ $ÄÁ [NO OPERATION] (ÉMPLIED) 1/2 ÄĂĐ $ÄÂ Í <- (Í)-1, (Á-Í) -> ÎÚĂ (ÁBSOLUTE,Ů) 3/7 ÎĎĐ $ÄĂ [NO OPERATION] (ÁBSOLUTE,Ř) 3/4'1 * ĂÍĐ $ÄÄ (Á - Í) -> ÎÚĂ (ÁBSOLUTE,Ř) 3/4'1 * ÄĹĂ $ÄĹ Í <- (Í) - 1 (ÁBSOLUTE,Ř) 3/7 ÄĂĐ $ÄĆ Í <- (Í)-1, (Á-Í) -> ÎÚĂ (ÁBSOLUTE,Ř) 3/7 * ĂĐŘ $Ĺ0 (Ř - Í) -> ÎÚĂ (ÉMMEDIATE) 2/2 * ÓÂĂ $Ĺ1 Á <- (Á) - Í - ~Ă (ÉND,Ř) 2/6 ÎĎĐ $Ĺ2 [NO OPERATION] (ÉMMEDIATE) 2/2 ÉÓÂ $Ĺ3 Í <- (Í) - 1,Á <- (Á)-Í-~Ă (ÉND,Ř) 3/8'1 * ĂĐŘ $Ĺ4 (Ř - Í) -> ÎÚĂ (Ú-ĐAGE) 2/3 * ÓÂĂ $Ĺ5 Á <- (Á) - Í - ~Ă (Ú-ĐAGE) 2/3 * ÉÎĂ $Ĺ6 Í <- (Í) + 1 (Ú-ĐAGE) 2/5 ÉÓÂ $Ĺ7 Í <- (Í) - 1,Á <- (Á)-Í-~Ă (Ú-ĐAGE) 2/5 * ÉÎŘ $Ĺ8 Ř <- (Ř) +1 (ÉMPLIED) 1/2 * ÓÂĂ $Ĺ9 Á <- (Á) - Í - ~Ă (ÉMMEDIATE) 2/2 * ÎĎĐ $ĹÁ [NO OPERATION] (ÉMPLIED) 1/2 ÓÂĂ $ĹÂ Á <- (Á) - Í - ~Ă (ÉMMEDIATE) 1/2 * ÓÂĂ $ĹÄ Á <- (Á) - Í - ~Ă (ÁBSOLUTE) 3/4 * ĂĐŘ $ĹĂ (Ř - Í) -> ÎÚĂ (ÁBSOLUTE) 3/4 * ÉÎĂ $ĹĹ Í <- (Í) + 1 (ÁBSOLUTE) 3/6 ÉÓÂ $ĹĆ Í <- (Í) - 1,Á <- (Á)-Í-~Ă (ÁBSOLUTE) 3/6 * ÂĹŃ $Ć0 IF Ú=1, ĐĂ = ĐĂ + OFFSET (ŇELATIVE) 2/2'2 * ÓÂĂ $Ć1 Á <- (Á) - Í - ~Ă ((ÉND),Ů) 2/5'1 ĘÁÍ $Ć2 [LOCKS UP MACHINE] (ÉMPLIED) 1/- ÉÓÂ $Ć3 Í <- (Í) - 1,Á <- (Á)-Í-~Ă ((ÉND),Ů) 2/8 ÎĎĐ $Ć4 [NO OPERATION] (Ú-ĐAGE,Ř) 2/4 * ÓÂĂ $Ć5 Á <- (Á) - Í - ~Ă (Ú-ĐAGE,Ř) 2/4 * ÉÎĂ $Ć6 Í <- (Í) + 1 (Ú-ĐAGE,Ř) 2/6 ÉÓÂ $Ć7 Í <- (Í) - 1,Á <- (Á)-Í-~Ă (Ú-ĐAGE,Ř) 2/6 * ÓĹÄ $Ć8 Ä <- 1 (ÉMPLIED) 1/2 * ÓÂĂ $Ć9 Á <- (Á) - Í - ~Ă (ÁBSOLUTE,Ů) 3/4'1 ÎĎĐ $ĆÁ [NO OPERATION] (ÉMPLIED) 1/2 ÉÓÂ $ĆÂ Í <- (Í) - 1,Á <- (Á)-Í-~Ă (ÁBSOLUTE,Ů) 3/7 ÎĎĐ $ĆĂ [NO OPERATION] (ÁBSOLUTE,Ř) 3/4'1 * ÓÂĂ $ĆÄ Á <- (Á) - Í - ~Ă (ÁBSOLUTE,Ř) 3/4'1 * ÉÎĂ $ĆĹ Í <- (Í) + 1 (ÁBSOLUTE,Ř) 3/7 ÉÓÂ $ĆĆ Í <- (Í) - 1,Á <- (Á)-Í-~Ă (ÁBSOLUTE,Ř) 3/7 '1 - ÁDD ONE IF ADDRESS CROSSES A PAGE BOUNDRY. '2 - ÁDD 1 IF BRANCH SUCCEEDS, OR 2 IF INTO ANOTHER PAGE. '3 - ÉF PAGE BOUNDRY CROSSED THEN ĐĂČ+1 IS JUST ĐĂČ '4 - ÓOURCES DISPUTED ON EXACT OPERATION, OR SOMETIMES DOES NOT WORK. '5 - ĆULL EIGHT BIT ROTATION (WITH CARRY) ÓOURCES: ĐROGRAMMING THE 6502, ŇODNEY ÚAKS, (C) 1983 ÓYBEX ĐAUL ĎJALA, ĐOST TO ĂOMP.ÓYS.ĂBM (PO87553@CS.TUT.FI / ALBERT@CC.TUT.FI) Ä ĘOHN ÍCKENNA, ĐOST TO ĂOMP.ÓYS.ĂBM (GUDJM@UNIWA.UWA.OZ.AU) ĂOMPILED BY ĂRAIG ÔAYLOR (DUCK@PEMBVAX1.PEMBROKE.EDU) ============================================================================== ÓIMPLE ČIRES ĚINE ÄRAWING ĐACKAGE FOR THE Ă-128 80-ĂOLUMN ÓCREEN ĂOPYRIGHT (C) 1992 ĂRAIG ÂRUCE 1. ÇŇÁĐČÉĂÓ ĐÁĂËÁÇĹ ĎÖĹŇÖÉĹ× ÔHE GRAPHICS PACKAGE THIS ARTICLE EXPLAINS IS ÂĚĎÁÄED INTO MEMORY AT ADDRESS $1300 ON BANK 15 AND HAS THREE ENTRY POINTS: $1300 = MOVE THE PIXEL CURSOR OR DRAW A LINE: .ÁŘ=X, .Ů=Y, .Ă=CMD $1303 = ACTIVATE GRAPHICS MODE AND CLEAR THE SCREEN $1306 = EXIT GRAPHICS MODE AND RELOAD THE CHARACTER SET ÔO MOVE THE PIXEL CURSOR TO THE START POINT OF A LINE, LOAD THE .ÁŘ REGISTERS WITH THE Ř COORDINATE (0-639), LOAD THE .Ů REGISTER WITH THE Ů COORDINATE (0-199), CLEAR THE CARRY FLAG, AND CALL $1300. (ÍAKE SURE THAT ÂANK 15 IS IN CONTEXT). ÔHIS CAN BE DONE IN ÂÁÓÉĂ AS FOLLOWS: ÓŮÓ 4864, Ř ÁÎÄ 255, Ř/256, Ů, 0 ÔO DRAW A LINE FROM THE PIXEL CURSOR LOCATION TO A GIVEN POINT, LOAD THE .ÁŘ AND .Ů REGISTERS LIKE BEFORE, SET THE CARRY FLAG, AND CALL $1300. ÔHE PIXEL CURSOR WILL THEN BE SET TO THE END POINT OF THE LINE JUST DRAWN, SO YOU DO NOT HAVE TO SET IT AGAIN IF YOU ARE DRAWING A CONTINUOUS OBJECT (LIKE A SQUARE). ÓŮÓ 4864, Ř ÁÎÄ 255, Ř/256, Ů, 1 ÔHE ACTIVATE AND EXIT ROUTINES ARE CALLED WITHOUT ANY PARAMETERS AND WORK VERY SIMPLY. ŮOU SHOULD BE SURE TO CALL EXIT BEFORE RETURNING TO THE PROGRAM EDITING MODE OR YOU WILL NOT BE ABLE TO SEE WHAT YOU ARE TYPING. Á ÂÁÓÉĂ DEMONSTRATION PROGRAM IS ALSO INCLUDED IN THE ŐŐ SECTION FOR THIS PACKAGE. ÉT STARTS BY PUTTING THE PIXEL CURSOR AT THE CENTER OF THE SCREEN AND THEN PICKS A RANDOM POINT TO DRAW TO, AND REPEATS UNTIL YOU PRESS A KEY TO STOP IT. ĆOR AN INTERESTING EFFECT, PUT A CALL TO $1303 IMMEDIATELY BEFORE THE CALL TO DRAW THE LINE. ÔHE POINT PLOTTING SPEED IS ABOUT 4,100 PIXELS PER SECOND AND THE LINE DRAWING SPEED IS A BIT SLOWER THAN THIS BECAUSE OF ALL OF THE CALCULATIONS THAT HAVE TO BE DONE TO DRAW A LINE. ÔHERE ARE FASTER PIXEL PLOTTING AND LINE DRAWING ALGORITHMS THAN THE ONES IMPLEMENTED HERE, BUT THAT IS MATERIAL FOR A FUTURE ARTICLE. 2. ÉÎÔŇĎÄŐĂÔÉĎÎ ÔĎ ÔČĹ ÖÄĂ ĐROGRAMMING THE 8563 ÖIDEO ÄISPLAY ĂONTROLLER IS QUITE STRAIGHT FORWARD. ŮOU ACCESS IT A BIT INDIRECTLY, BUT IT CAN STILL BE DONE AT RELATIVELY HIGH SPEEDS USING MACHINE LANGUAGE. ÔHE ÖÄĂ CONTAINS 37 CONTROL REGISTERS AND FROM 16Ë TO 64Ë OF DEDICATED DISPLAY MEMORY THAT IS SEPARATE FROM THE MAIN PROCESSOR. ÔHE MEMORY MUST BE ACCESSED THROUGH THE ÖÄĂ REGISTERS. ÔHE IMPORTANT ÖÄĂ REGISTERS FOR THIS EXERCISE ARE: ŇĹÇ ÂÉÔÓ ÄĹÓĂ --- ---- ---- $12 7-0 ÖÄĂ ŇÁÍ ADDRESS HIGH BYTE $13 7-0 ÖÄĂ ŇÁÍ ADDRESS LOW BYTE $18 7 ÂLOCK COPY / BLOCK FILL MODE SELECT $19 7 ÂITMAP / ĂHARACTER MODE SELECT $19 6 ĂOLOR / ÍONOCHROME MODE SELECT $1A 7-4 ĆOREGROUND COLOR $1A 3-0 ÂACKGROUND COLOR $1E 7-0 ĂOPY / FILL REPETITION COUNT $1F 7-0 ÖÄĂ ŇÁÍ DATA READ / WRITE ŮOU ACCESS THE ÖÄĂ CHIP REGISTERS THOUGH ADDRESSES $ÄĆ00 AND $ÄĆ01 ON BANK 15. ĚOCATION $ÄĆ00 SELECTS THE ÖÄĂ REGISTER TO USE ON WRITE AND RETURNS THE ÖÄĂ STATUS ON READ. ÔHE ONLY IMPORTANT STATUS INFORMATION IS BIT 7 (VALUE $80) WHICH IS THE "READY" FLAG. ÔHE FOLLOWING TWO SUBROUTINES READ OR WRITE THE VALUE IN .Á TO ÖÄĂ REGISTER NUMBER .Ř: ÖDCŇEAD: STX $DF00 ÖDC×RITE: STX $DF00 ×AITĚOOP: BIT $DF00 ×AITĚOOP: BIT $DF00 BPL ×AITĚOOP BPL ×AITĚOOP LDA $DF01 STA $DF01 RTS RTS ĎNCE THE CURRENT ÖÄĂ REGISTER IS SELECTED AT $DF00, IT REMAINS SELECTED. ŮOU MAY READ OR WRITE IT THOUGH $DF01 AS MANY TIMES AS YOU LIKE AS LONG AS YOU WAIT FOR THE ÖÄĂ TO BE "READY" BETWEEN ACCESSES. ÉN ORDER TO ACCESS THE ÖÄĂ ŇÁÍ, YOU MUST FIRST PUT THE HIGH AND LOW BYTES OF THE ÖÄĂ ŇÁÍ ADDRESS INTO REGISTERS $12 AND $13 (HIGH BYTE FIRST) AND THEN READ OR WRITE THROUGH REGISTER $1F TO READ OR WRITE THE DATA IN THE ÖÄĂ ŇÁÍ. ÁFTER EACH ACCESS TO REGISTER $1F, THE ÖÄĂ ŇÁÍ ADDRESS IS INCREMENTED BY ONE. ÓO, IF YOU REPEATEDLY READ OR WRITE TO REGISTER $1F YOU CAN READ OR WRITE A CHUNK OF ÖÄĂ MEMORY VERY QUICKLY. 3. ĹÎÔĹŇÉÎÇ ÇŇÁĐČÉĂÓ ÍĎÄĹ ÁCTIVATING THE GRAPHICS MODE OF THE ÖÄĂ IS VERY SIMPLE - YOU JUST HAVE TO SET BIT 7 OR ÖÄĂ REGISTER $19 AND POOF! ŮOU SHOULD ALSO CLEAR BIT 6 OF THAT REGISTER TO DISABLE THE CHARACTER COLOR MODE. ÔHIS GRAPHICS PACKAGE SUPPORTS ONLY MONOCHROME GRAPHICS SINCE THE STANDARD 16Ë ÖÄĂ DOES NOT HAVE ENOUGH SPACE TO HOLD BOTH THE BITMAP AND THE 8*8 PIXEL CELL ATTRIBUTES. ÔHE 640*200 PIXEL DISPLAY TAKES 128,000 BITS OR 16,000 BYTES. ÔHIS LEAVES 384 BYTES OF ÖÄĂ ŇÁÍ THAT IS NOT NEEDED BY THE BITMAP BUT IT IS NOT LARGE ENOUGH TO DO ANYTHING WITH, SO IT IS WASTED. ×HEN YOU DISABLE THE CHARACTER COLOR MODE, THE ÖÄĂ TAKES ITS FOREGROUND AND BACKGROUND COLOR VALUES FROM REGISTER $1A. ÔHE FOREGROUND COLOR IS WHAT COLOR THE "1" BITS IN THE BITMAP WILL BE DISPLAYED IN AND THE BACKGROUND COLOR, THE "0" BITS. ÎOW THAT THE BITMAP MODE IS SET UP, WE MUST CLEAR THE ÖÄĂ MEMORY LOCATIONS 0 TO 15999 (DECIMAL) TO CLEAR THE BITMAP SCREEN. ÔHIS CAN BE DONE VERY QUICKLY USING THE ÖÄĂ FILL MODE. ÉF YOU POKE A VALUE INTO ÖÄĂ REGISTER NUMBER $1E, THE ÖÄĂ WILL FILL ITS MEMORY FROM THE LOCATION CURRENTLY IN THE ÖÄĂ ŇÁÍ ADDRESS REGISTERS FOR THE NUMBER OF BYTES YOU JUST POKED INTO REGISTER $1E WITH THE VALUE THAT YOU LAST POKED INTO THE ÖÄĂ ŇÁÍ DATA REGISTER. (ÔHIS IS ASSUMING THAT "FILL" MODE IS SELECTED IN REGISTER $18). ÉF YOU POKE A 0 INTO THE REPEAT REGISTER IT MEANS TO FILL 256 BYTES. ÓO, TO CLEAR THE BITMAP, POKE A ZERO INTO BOTH OF THE ÖÄĂ ŇÁÍ ADDRESS REGISTERS SINCE THE BITMAP STARTS AT LOCATION 0. ÔHEN POKE A VALUE OF 0 INTO ÖÄĂ ŇÁÍ DATA REGISTER. ÔHIS SETS THE FILL VALUE TO 0 AND POKES THE FIRST ÖÄĂ ŇÁÍ LOCATION. ÔHEN, GO INTO A LOOP AND PUT A ZERO INTO THE ÖÄĂ REPEAT REGISTER 63 TIMES. ÔHIS WILL FILL 63 CONTIGUOUS CHUNKS OF 256 BYTES EACH. ×E END UP FILLING 16,129 BYTES, BUT THAT IS NOT A PROBLEM SINCE WE HAVE 384 "SAFETY" BYTES AT THE END OF THE BITMAP. ÉNTERNALLY, THE ÖÄĂ WILL FILL ITS MEMORY AT A RATE OF ABOUT 1 ÍEGABYTE PER SECOND (IF É REMEMBER MY TEST RESULTS CORRECTLY), SO CLEARING THE SCREEN IS A ĐÄŃ OPERATION. 4. ĹŘÉÔÉÎÇ ÇŇÁĐČÉĂÓ ÍĎÄĹ ÔO EXIT FROM GRAPHICS MODE WE HAVE TO RELOAD THE CHARACTER SET FROM THE ŇĎÍ ON BANK 14 AND WE HAVE TO GO BACK INTO CHARACTER MODE AND CLEAR THE TEXT SCREEN. ÔHE KERNEL PROVIDES ITS OWN CHARACTER RELOAD ROUTINE SO É USED THAT. ÔHE ONLY PROBLEM WITH IT IS THAT IT IS A LOT SLOWER THAN IT HAS TO BE. ÉT TAKES ABOUT 0.45 SECONDS WHEREAS THE SAME JOB CAN BE DONE IN ABOUT 0.09 SECONDS. ÔHE KERNEL IS SO SLOW BECAUSE IT USES THE KERNEL ÉÎÄĆĹÔĂČ NONSENSE. ÔHEN YOU JUST SET THE BITMAP MODE BIT TO ZERO AND THE CHARACTER COLOR MODE TO ONE. ÔHIS GETS YOU BACK TO NORMAL CHARACTER MODE. ŮOU ALSO HAVE TO CLEAR THE TEXT SCREEN SINCE IT WILL BE FILLED WITH GARBAGE FROM THE GRAPHING. 5. ĐĎÉÎÔ ĐĚĎÔÔÉÎÇ ÔHE PIXELS ON THE SCREEN ACCESSED BY THEIR Ř AND Ů COORDINATES, 0 <= Ř <= 639, 0 <= Ů <= 199. ÔHE FORMULA TO CALCULATE THE BYTE ADDRESS IN THE ÖÄĂ ŇÁÍ GIVEN THE Ř AND Ů COORDINATES IS MADE SIMPLE BY THE MAPPING OF BYTES TO THE PIXELS ON THE SCREEN. ÔHE BYTES OF ÖÄĂ MEMORY GO ACROSS THE SCREEN RATHER THAN IN 8*8 CELLS LIKE THE ÖÉĂ SCREEN. ĹACH PIXEL ROW IS DEFINED BY 80 CONSECUTIVE BYTES OF ÖÄĂ ŇÁÍ. ÔHE FORMULA FOR THE BYTE ADDRESS OF A PIXEL IS: ÁÄ=Ů*80+ÉÎÔ(Ř/8), AND THE FORMULA FOR THE BIT NUMBER IS SIMPLY ÂÉ=Ř ÁÎÄ 7. ÔHE BIT NUMBER CAN BE USED AS AN INDEX INTO A TABLE OF BIT VALUES: [$80,$40,$20,$10,$08,$04,$02,$01], SUCH THAT INDEX 0 CONTAINS $80, SINCE THE HIGHEST BIT IS THE LEFTMOST BIT. ĂALCULATING THE BIT NUMBER AND LOOKING UP THE BIT VALUE IS VERY EASY TO DO IN MACHINE LANGUAGE, BUT THE BYTE ADDRESS CALCULATION REQUIRES A LITTLE MORE WORK. ĆIRST WE HAVE TO MULTIPLY THE Ů VALUE BY 80, USING A 16-BIT WORD FOR STORAGE. ÔHIS IS DONE BY SHIFTING THE Ů VALUE LEFT TWICE, ADDING THE ORIGINAL Ů VALUE, AND SHIFTING LEFT FOUR MORE TIMES. ÔHEN WE HAVE TO SHIFT THE Ř VALUE RIGHT BY THREE USING A 16-BIT WORD FOR STORAGE TO GET ÉÎÔ(Ř/8), AND WE ADD THE TWO RESULTS TOGETHER AND WE HAVE THE BYTE ADDRESS. ÔO PLOT THE POINT, WE HAVE TO PEEK INTO THE ÖÄĂ ŇÁÍ AT THE BYTE ADDRESS TO SEE WHAT IS "BEHIND" THE PIXEL WE WANT TO PLOT. ÔHEN ĎŇ THE NEW BIT VALUE ON TO THE "BACKGROUND" VALUE AND POKE THE RESULT BACK INTO ÖÄĂ ŇÁÍ AT THE BYTE ADDRESS. ŐNFORTUNATELY, SINCE THE ÖÄĂ ŇÁÍ ADDRESS REGISTER AUTO-INCREMENTS AFTER EACH REFERENCE, WE WILL HAVE TO SET IT TWICE - ONCE FOR THE READ AND ONCE FOR THE WRITE. ÔHAT MEANS THAT THE ÖÄĂ REGISTERS HAVE TO BE ACCESSED SIX TIMES FOR EACH PIXEL. ĆORTUNATELY, THE ÖÄĂ OPERATES AT ITS HIGHEST SPEED IN MONOCHROME BITMAP MODE (IT HAS LESS WORK TO DO THAN IN COLOR CHARACTER MODE, SO IT IS ABLE TO PAY MORE ATTENTION TO THE ĂĐŐ). ĹFFECTS OTHER THAN JUST PLOTTING THE POINT CAN BE ACHIEVED BY USING FUNCTIONS OTHER THAN ĎŇ TO PUT THE POINT ON THE BACKGROUND. ĹĎŇ WOULD "FLIP" THE PIXEL, AND ÁÎÄ-ÎĎÔ (ACHIEVED BY ĚÄÁ BITVAL : ĹĎŇ #$FF : ÁÎÄ BACKGROUND) WOULD ERASE THE PIXEL. 6. ĚÉÎĹ ÄŇÁ×ÉÎÇ ÔHE LINE DRAWING ROUTINE THAT IS IMPLEMENTED IN THE PACKAGE IS GIVEN BY THE FOLLOWING ÂÁÓÉĂ CODE (IN FACT, É PROGRAMMED IT IN ÂÁÓÉĂ FIRST TO GET IT WORKING; OF COURSE, THE ÂÁÓÉĂ VERSION IS AS SLOW AS HELL): 10 DX=X-LX:DY=Y-LY 20 IF ABS(DX)>ABS(DY) THEN BEGIN R=DX:GY=DY/ABS(DX):GX=SGN(DX) 30 BEND:ELSE R=DY:GX=DX/ABS(DY):GY=SGN(DY) 40 PX=LX+0.5:PY=LY+0.5 50 FORI=1TO ABS(R): <ĐĚĎÔ ĐŘ,ĐŮ> :PX=PX+GX:PY=PY+GY:NEXT 60 LX=X:LY=Y ÔHIS IMPLEMENTS THE ÂASIC ÉNCREMENTAL ÁLGORITHM FOR RASTER LINE DRAWING. ÔHE "LX" AND "LY" ARE THE POSITION OF THE PIXEL CURSOR AND "X" AND "Y" ARE THE COORDINATES TO DRAW THE LINE TO. ÔHE "DX" AND "DY" ARE THE DIFFERENCES IN THE Ř AND Ů DIRECTIONS. ÔHE IDEA IS THAT WE WILL INCREMENT THE PIXEL CURSOR BY A CONSTANT OF 1 IN ONE DIRECTION AND BY A FRACTION 0.0 <= G <= 1.0 IN THE OTHER DIRECTION. ÔHIS FRACTION IS ACTUALLY THE SLOPE OF THE LINE. ĚINES 20 AND 30 FIGURE OUT THE INCREMENTS FOR THE Ř AND Ů DIRECTIONS ("GX" AND "GY"). ÔHESE ARE SIGNED FRACTIONAL NUMBERS ON THE RANGE -1.0 <= G <= 1.0. ×E CHECK THE "DX" AND "DY" TO SEE WHICH HAS THE GREATEST ABSOLUTE VALUE AND THAT WILL BE THE DIRECTION THAT IS INCREMENTED BY 1, 0, OR -1 AND THE OTHER DIRECTION WILL INCREMENT BY THE (FRACTIONAL) SLOPE OF THE LINE WITH RESPECT TO THE OTHER DIRECTION. ĚINE 40 STARTS THE PLOTTING AT THE CURRENT PIXEL CURSOR LOCATION ĐĚŐÓ 0.5. ×E ADD 1/2 TO THE Ř AND Ů POSITIONS TO "CENTER" ONTO THE PIXEL CELL. ÉF WE DIDN'T DO THIS, WE WOULD NOTICE DIS-SYMMETRY IN PLOTTING TO THE LEFT AND TO THE RIGHT. ĆOR EXAMPLE, 50.0 - 0.3 = 49.7 AND 50.0 + 0.3 = 50.3. ÉF WE TRUNCATE THESE VALUES, GOING LEFT BY 0.3 MOVES US TO POSITION 49 WHEREAS GOING RIGHT BY 0.3 MAKES US STAY IN THE SAME POSITION. ÔHIS IS DIS-SYMMETRY AND MAKES PLOTS LOOK A BIT OFF. ÁDDING 0.5 CORRECTS THE PROBLEM. ĚINE 50 GOES INTO A LOOP FOR THE LONGEST DIMENSION OF THE LINE (THE ONE INCREMENTED BY 1). ÔHE <ĐĚĎÔ ĐŘ,ĐŮ> IS NOT EXACTLY ÂÁÓÉĂ; YOU SUBSTITUTE THE CALL TO THE POINT PLOT ROUTINE DESCRIBED IN THE PREVIOUS SECTION. ÉT REPEATEDLY ADDS THE Ř AND Ů INCREMENT VALUES UNTIL THE LINE IS FINISHED. ÔHIS ALGORITHM DRAWS THE LINE IN THE DIRECTION THAT YOUR END POINTS IMPLY. 6.1. ĆŇÁĂÔÉĎÎÁĚ ÎŐÍÂĹŇ ŇĹĐŇĹÓĹÎÔÁÔÉĎÎ ÔHERE ARE ONLY TWO REAL COMPLICATIONS TO THE MACHINE LANGUAGE IMPLEMENTATION ARE THE REPRESENTATION OF THE SIGNED FRACTIONAL NUMBERS AND THE DIVISION OF THE FRACTIONAL NUMBERS. ÔO REPRESENT THE NUMBERS É USE A 32-BIT FORMAT WITH A 16-BIT SIGNED INTEGER PORTION (-32768 TO +32767) AND A 16-BIT FRACTIONAL PORTION (0.0 TO 0.99998474 IN 0.00001526 INCREMENTS). ÔHE WEIGHT VALUES OF THE BIT POSITIONS ARE AS FOLLOWS: ĐĎÓ 31 ... 22 21 20 19 18 17 16 15 14 13 12 11 10 9 ... 0 ÖÁĚ 32768 ... 64 32 16 8 4 2 1 1/2 1/4 1/8 1/16 1/32 1/64 1/128 ...1/65536 ĆOR EXAMPLE, 0...00001011101.10011010000...0 (NOTICE THE ÂÉÎÁŇŮ POINT) IS 64 + 16 + 8 + 4 + 1 + 1/2 + 1/16 + 1/32 + 1/128 = 93.6015625 IN DECIMAL. ĎR, AS A SHORT CUT, YOU CAN CONSIDER THE INTEGER 16 BITS AND THE FRACTIONAL 16 BITS AS INDEPENDENT WORDS AND ADD 1/65536TH OF THE SECOND TO THE FIRST. ÔHUS, FOR THE EXAMPLE ABOVE, THE QUANTITY IS 93 + (32768+4096+2048+512)/65536 = 93.6015625. (ÇOOD, THEY BOTH MATCH). ÔHE FIRST CALCULATION USES TRUE BASE 2 WHEREAS THE SECOND CALCULATION USES BASE 65536. ÔWO'S COMPLEMENT REPRESENTATION IS USED TO ACHIEVE SIGNEDNESS (,ĐARK!). ×E SHOULD ALL KNOW ABOUT TWO'S COMP. ×ELL, IT WORKS JUST FINE FOR FRACTIONAL BINARY NUMBERS AS WELL. ÉN FACT, IT MAKES NO DIFFERENCE AT ALL. ŮOU CAN JUST THINK OF THE QUANTITY AS AN INTEGER NUMBER OF 65536'S OF A PIXEL AND YOU GET THE INTEGER OPERATIONS OF COMPLEMENT, ADD, AND SUBTRACT FOR FREE. ÔHE EASY WAY TO GET THE TWO'S COMP. REPRESENTATION OF A NUMBER IS TO TAKE THE POSITIVE BINARY IMAGE OF THE NUMBER AND SUBTRACT IT FROM 0 (THIS MAKES PERFECT SENSE SINCE 0 - X = -X). ĆRACTIONAL BINARY DIVISION IS A LITTLE MORE COMPLICATED. ÔHERE IS NO PROBLEM WITH THE BINARY POINT, SINCE THE LAWS OF MATHEMATICS SAY WE CAN MULTIPLY THE TOP AND BOTTOM BY THE SAME QUANTITY (LIKE 65536) WITHOUT CHANGING THE RESULT, BUT HANDLING THE TWO'S COMPLEMENT IS A PROBLEM. ×HAT É DID WAS FIGURE OUT WHAT THE SIGN OF THE RESULT OF THE DIVISION WAS GOING TO BE (BY ĹĎŇING THE SIGN BITS TOGETHER) AND THEN CONVERTED THE TWO OPERANDS TO THEIR POSITIVE VALUE IF THEY WERE ORIGINALLY NEGATIVE. ÔHIS LETS ME PERFORM A 32-BIT UNSIGNED DIVISION OPERATION AND THEN É CONVERT THE RESULT TO A NEGATIVE IF THE RESULT IS SUPPOSED TO BE NEGATIVE. ÔHE 32-BIT DIVIDE IS NOT ALL THAT COMPLICATED; IT IS DONE THE SAME WAY THAT YOU WOULD DO IT ON PAPER (REMEMBER THOSE DAYS) EXCEPT YOU USE BINARY DIGITS. ÔHE DIVIDE SUBROUTINE DOES NOT EXACTLY RIVAL SUPERCOMPUTER SPEEDS, BUT IT DOES GET THE JOB DONE. 6.2. ÍÁĂČÉÎĹ ĚÁÎÇŐÁÇĹ ĎĐĹŇÁÔÉĎÎ ×HILE DRAWING THE LINE, THE Ř AND Ů COORDINATES ARE 32-BIT SIGNED FRACTIONAL NUMBERS AS WELL AS THE "GX" AND "GY" VECTOR COMPONENTS ("GO" VALUES). ĚINES 20 AND 30 REQUIRE QUITE A BIT OF WORK IN 6502 MACHINE LANGUAGE AND USE THE 32-BIT ADD, SUBTRACT, 2'S COMPLEMENT, AND DIVIDE OPERATIONS DESCRIBED IN THE PREVIOUS SECTION. ÔO FIND THE ÁÂÓOLUTE VALUE OF A NUMBER, CHECK TO SEE WHETHER IT IS POSITIVE OR NEGATIVE. ÉF IT IS POSITIVE, YOU ARE DONE. ÉF IT IS NEGATIVE, JUST DO A 2'S COMPLEMENT ON IT (MAKES SENSE: 0 - (-X) = X). ĚINE 40 IS DONE BY SIMPLY TAKING THE PIXEL CURSOR Ř AND Ů COORDINATES (WHICH ARE STORED AS UNSIGNED INTEGERS AND ARE REMEMBERED BETWEEN LINE DRAW CALLS) AND PUT THEM INTO THE HIGH WORD OF A 32-BIT FIELD AND THEN PUT $8000 (32768) INTO THE LOW WORD (WHICH GIVES Ö + 1/2). ĚINE 50 IS EASILY IMPLEMENTED AS A LOOP THAT DECREMENTS THE "R" WORD UNTIL IT REACHES ZERO, WHILE CALLING THE POINT PLOT ROUTINE AND DOING THE 32-BIT ADD TO ADD THE "G" VALUES TO THE Ř AND Ů COORDINATES. ×HEN THE LINE IS FINISHED, THE FINAL Ř AND Ů COORDINATES ARE PUT BACK INTO THE PIXEL CURSOR POSITION STORAGE AND THE PACKAGE IS READY FOR THE NEXT CALL. 7. ĂĎÎĂĚŐÓÉĎÎ ČA! ÔHIS AIN'T NO FORMAL PAPER SO É DON'T HAVE TO WRITE A CONCLUSION. ÓO THERE! [ĹD.ÎOTE - ČE IS CURRENTLY WORKING ON HIS ÍASTERS THESIS, SO YOU'LL HAVE TO PARDON 'EM HERE.. (GRIN) ] ================================================================================ ;***************************************************************************** ;* "ČÉŇĹÓ80.ÂÉÎ" HIRES LINE PLOTTING PACKAGE FOR THE ĂOMMODORE 128 80-COL * ;* SCREEN. * ;* * ;* ÔHIS PACKAGE CONTAINS A COUPLE OF IRREGULARITIES THAT É DISCOVERED * ;* WHILE É WAS COMMENTING IT. É LEFT THEM IN RATHER THAN START ALL OVER, * ;* SINCE THIS PACKAGE WAS WRITTEN WITH A MONITOR RATHER THAN AN ASSEMBLER. * ;***************************************************************************** ;***************************************************************************** ;* PACKAGE ENTRY POINTS * ;***************************************************************************** .$1300 [4C 01 15] JMP $1501 ;JMP TO DRAW LINE/POSITION PIXEL CURSOR .$1303 [4C 11 13] JMP $1311 ;JMP TO ENTER HIRES MODE .$1306 [4C 48 13] JMP $1348 ;JMP TO EXIT HIRES MODE .$1309 [4C 10 13] JMP $1310 ;RESERVED .$130C [4C 10 13] JMP $1310 ;RESERVED .$130F: $B3 ;LIBRARY LOADED IDENTIFIER .$1310 [60 ] RTS ;***************************************************************************** ;* ENTER HIRES MODE * ;***************************************************************************** .$1311 [A9 00 ] LDA #$00 ;SWITCH TO BANK 15 (KERNAL BANK) .$1313 [8D 00 FF] STA $FF00 .$1316 [A9 E0 ] LDA #$E0 ;SET COLOR TO LIGHT GREY ON BLACK .$1318 [A2 1A ] LDX #$1A .$131A [20 CC CD] JSR $CDCC .$131D [A9 87 ] LDA #$87 ;ENTER BITMAP MODE (NOTE - FOR VERSION 2 ÖÄĂ) .$131F [A2 19 ] LDX #$19 .$1321 [20 CC CD] JSR $CDCC .$1324 [A9 00 ] LDA #$00 ;SET ÖÄĂ ŇÁÍ ADDRESS HIGH .$1326 [A2 12 ] LDX #$12 .$1328 [20 CC CD] JSR $CDCC .$132B [E8 ] INX ;SET ÖÄĂ ŇÁÍ ADDRESS LOW .$132C [20 CC CD] JSR $CDCC .$132F [A9 00 ] LDA #$00 ;SET ÖÄĂ ŇÁÍ DATA REGISTER TO $00 .$1331 [20 CA CD] JSR $CDCA .$1334 [A9 20 ] LDA #$20 ;SELECT BLOCK FILL MODE .$1336 [A2 18 ] LDX #$18 .$1338 [20 CC CD] JSR $CDCC .$133B [A9 00 ] LDA #$00 ;FILL 256*63 ÖÄĂ BYTES WITH 0 .$133D [A2 1E ] LDX #$1E ; TO CLEAR THE HIRES SCREEN .$133F [A0 3F ] LDY #$3F .$1341 [20 CC CD] JSR $CDCC .$1344 [88 ] DEY .$1345 [D0 FA ] BNE $1341 .$1347 [60 ] RTS ;***************************************************************************** ;* EXIT HIRES MODE * ;***************************************************************************** .$1348 [20 0C CE] JSR $CE0C ;RELOAD THE CHARACTER SETS .$134B [A9 93 ] LDA #$93 ;CLEAR THE TEXT SCREEN .$134D [20 D2 FF] JSR $FFD2 .$1350 [A2 19 ] LDX #$19 ;RESTORE COLOR TEXT MODE .$1352 [A9 47 ] LDA #$47 .$1354 [4C CC CD] JMP $CDCC ;***************************************************************************** ;*CALCULATE THE BITMAP BYTE ADDRESS AND BIT VALUE FOR PIXEL GIVEN X=.ÁŘ,Y=.Ů * ;***************************************************************************** .$1357 [84 FA ] STY $FA ;SAVE .Á AND .Ů .$1359 [85 FC ] STA $FC .$135B [98 ] TYA ;PUT PIXEL CURSOR Y POSITION INTO .Á .$135C [A0 00 ] LDY #$00 ;CLEAR PIXEL CURSOR Y POSITION HIGH BYTE .$135E [84 FB ] STY $FB .$1360 [0A ] ASL A ;MULTIPLY PIXEL CURSOR Y BY 2 GIVING Y*2 .$1361 [26 FB ] ROL $FB ; AND WE MUST SHIFT THE HIGH BYTE TO .$1363 [0A ] ASL A ;AGAIN, GIVING Y*4 .$1364 [26 FB ] ROL $FB .$1366 [18 ] CLC ;ADD THE ORIGINAL Y, GIVING Y*5 .$1367 [65 FA ] ADC $FA .$1369 [90 02 ] BCC $136D .$136B [E6 FB ] INC $FB .$136D [0A ] ASL A ;MULTIPLY BY 2 AGAIN, GIVING Y*10 .$136E [26 FB ] ROL $FB .$1370 [0A ] ASL A ;AGAIN, GIVING Y*20 .$1371 [26 FB ] ROL $FB .$1373 [0A ] ASL A ;AGAIN, GIVING Y*40 .$1374 [26 FB ] ROL $FB .$1376 [0A ] ASL A ;AGAIN, GIVING Y*80: HA! WE ARE DONE .$1377 [26 FB ] ROL $FB .$1379 [85 FA ] STA $FA ;SAVE LOW BYTE OF Y*80 .$137B [A5 FC ] LDA $FC ;RESTORE X COORDINATE LOW BYTE .$137D [86 FD ] STX $FD ;SET UP X COORDINATE HIGH BYTE .$137F [46 FD ] LSR $FD ;DIVIDE THE X COORDINATE BY 2 GIVING X/2 .$1381 [6A ] ROR A ; WE MUST ROR THE HIGH BYTE, THEN THE LOW .$1382 [46 FD ] LSR $FD ;AGAIN, GIVING X/4 .$1384 [6A ] ROR A .$1385 [46 FD ] LSR $FD ;AGAIN, GIVING X/8: DONE .$1387 [6A ] ROR A .$1388 [18 ] CLC ;NOW ADD Y*80 AND X/8 .$1389 [65 FA ] ADC $FA .$138B [85 FA ] STA $FA .$138D [A5 FD ] LDA $FD .$138F [65 FB ] ADC $FB .$1391 [85 FB ] STA $FB ;GIVING US THE PIXEL BYTE ADDRESS IN ($FA) .$1393 [A5 FC ] LDA $FC ;GET X MOD 8 .$1395 [29 07 ] AND #$07 ; HA! WE CAN JUST EXTRACT THE LOW THREE BITS .$1397 [AA ] TAX .$1398 [BD 9E 13] LDA $139E,X ;LOOK UP THE BIT VALUE IN THE TABLE .$139B [85 FC ] STA $FC ; AND SAVE IT AT $FC .$139D [60 ] RTS ;EXIT WITH ADDRESS IN ($FA) AND VALUE IN $FC ;***************************************************************************** ;* BIT VALUE TABLE * ;***************************************************************************** .$139E: $80 $40 $20 $10 ;BIT VALUES STORED LEFT TO RIGHT .$13A2: $08 $04 $02 $01 .$13A6 [00 ] BRK ;FILLER - É FORGET WHY É PUT IT HERE .$13A7 [00 ] BRK ;***************************************************************************** ;* PLOT PIXEL AT X=.ÁŘ, Y=.Ů ON BITMAP SCREEN * ;***************************************************************************** .$13A8 [20 57 13] JSR $1357 ;CALCULATE THE PIXEL ADDRESS AND VALUE .$13AB [A5 FB ] LDA $FB ;SET ÖÄĂ ŇÁÎ ADDRESS HIGH TO PIXEL ADDRESS .$13AD [A2 12 ] LDX #$12 .$13AF [20 CC CD] JSR $CDCC .$13B2 [A5 FA ] LDA $FA ;SET ÖÄĂ ŇÁÍ ADDRESS LOW TO PIXEL ADDRESS .$13B4 [E8 ] INX .$13B5 [20 CC CD] JSR $CDCC .$13B8 [20 D8 CD] JSR $CDD8 ;PEEK THE ÖÄĂ ŇÁÍ ADDRESS .$13BB [05 FC ] ORA $FC ;ĎŇ ON THE NEW PIXEL VALUE .$13BD [A8 ] TAY ; AND SAVE THE RESULT (BYTE TO POKE BACK) .$13BE [A5 FB ] LDA $FB ;RESET THE ÖÄĂ ŇÁÍ ADDRESS TO THE PIXEL .$13C0 [A2 12 ] LDX #$12 ; ADDRESS; THIS IS NECESSARY SINCE THE .$13C2 [20 CC CD] JSR $CDCC ; ÖÄĂ WILL INCREMENT ITS ŇÁÍ ADDRESS ON .$13C5 [A5 FA ] LDA $FA ; EVERY ACCESS .$13C7 [E8 ] INX .$13C8 [20 CC CD] JSR $CDCC .$13CB [98 ] TYA .$13CC [4C CA CD] JMP $CDCA ;AND POKE THE NEW PIXEL BYTE VALUE ;***************************************************************************** ;* PERFORM THE UNSIGNED 32-BIT DIVIDE WITH 16-BIT DENOMINATOR (BOTTOM) * ;* [$63 $62 $61 $60] IS THE NUMERATOR (TOP) * ;* [$51 $50] IS THE DENOMINATOR (BOTTOM) * ;* [$67 $66 $65 $64] IS THE QUOTIENT (RESULT) * ;* [$54 $53 $52] IS THE REMAINDER * ;***************************************************************************** .$13CF [A9 00 ] LDA #$00 ;SET THE RESULT TO 0 .$13D1 [85 64 ] STA $64 .$13D3 [85 65 ] STA $65 .$13D5 [85 66 ] STA $66 .$13D7 [85 67 ] STA $67 .$13D9 [85 52 ] STA $52 ;CLEAR THE REMAINDER .$13DB [85 53 ] STA $53 .$13DD [85 54 ] STA $54 .$13DF [A2 20 ] LDX #$20 ;SET THE LOOP COUNT TO 32 BITS .$13E1 [06 60 ] ASL $60 ;SHIFT OUT THE HIGH BIT OF THE NUMERATOR .$13E3 [26 61 ] ROL $61 .$13E5 [26 62 ] ROL $62 .$13E7 [26 63 ] ROL $63 .$13E9 [26 52 ] ROL $52 ;SHIFT IT INTO THE REMAINDER .$13EB [26 53 ] ROL $53 .$13ED [26 54 ] ROL $54 .$13EF [A5 54 ] LDA $54 ;CHECK IF THE REMAINDER IS >= THE DENOMINATOR .$13F1 [D0 0A ] BNE $13FD .$13F3 [A5 52 ] LDA $52 .$13F5 [C5 50 ] CMP $50 .$13F7 [A5 53 ] LDA $53 .$13F9 [E5 51 ] SBC $51 .$13FB [90 11 ] BCC $140E ;IF NOT, GO TO NEXT BIT .$13FD [38 ] SEC ;SUBRACT THE DENOMINATOR FROM THE REMAINDER .$13FE [A5 52 ] LDA $52 .$1400 [E5 50 ] SBC $50 .$1402 [85 52 ] STA $52 .$1404 [A5 53 ] LDA $53 .$1406 [E5 51 ] SBC $51 .$1408 [85 53 ] STA $53 .$140A [B0 02 ] BCS $140E .$140C [C6 54 ] DEC $54 .$140E [26 64 ] ROL $64 ;SHIFT A "1" BIT INTO THE DENOMINATOR. ÎOTE .$1410 [26 65 ] ROL $65 ; THE FIRST "ROL" SHOULD HAVE BEEN PRECEEDED .$1412 [26 66 ] ROL $66 ; BY A "SEC"; THIS IS A ÂŐÇ! ČOWEVER, IT .$1414 [26 67 ] ROL $67 ; WILL FAIL ONLY IF DENOM >=32768 WHICH ; CANNOT HAPPEN IN THIS APPLICATION. .$1416 [CA ] DEX ;GO ON TO THE NEXT BIT .$1417 [D0 C8 ] BNE $13E1 .$1419 [60 ] RTS ;***************************************************************************** ;* GET THE ABSOLUTE VALUE OF THE 2'S COMP NUMBER IN .ÁŮ -> .ÁŮ * ;***************************************************************************** .$141A [84 50 ] STY $50 .$141C [A6 50 ] LDX $50 .$141E [10 10 ] BPL $1430 ;IF THE NUMBER IS POSITIVE, EXIT .$1420 [38 ] SEC ;ELSE TAKE THE 2'S COMPLEMENT OF THE NEGATIVE .$1421 [85 50 ] STA $50 ; VALUE TO GET THE POSITIVE VALUE .$1423 [A9 00 ] LDA #$00 .$1425 [E5 50 ] SBC $50 .$1427 [48 ] PHA .$1428 [84 50 ] STY $50 .$142A [A9 00 ] LDA #$00 .$142C [E5 50 ] SBC $50 .$142E [A8 ] TAY .$142F [68 ] PLA .$1430 [60 ] RTS ;***************************************************************************** ;* PERFORM THE FRACTIONAL SIGNED 32-BIT DIVIDE * ;***************************************************************************** .$1431 [48 ] PHA ;REMEMBER THE SIGN OF THE RESULT .$1432 [A9 00 ] LDA #$00 ;SET THE NUMERATOR FRACTIONAL PORTION TO .0 .$1434 [85 60 ] STA $60 .$1436 [85 61 ] STA $61 .$1438 [20 CF 13] JSR $13CF ;32-BIT DIVIDE .$143B [68 ] PLA ;IF THE SIGN OF THE RESULT IS SUPPOSED TO BE .$143C [10 19 ] BPL $1457 ; POSITIVE, THEN EXIT .$143E [38 ] SEC ;IF THE SIGN OF THE RESULT IS NEGATIVE, TAKE .$143F [A9 00 ] LDA #$00 ; GET THE 2'S COMPLEMENT OF THE POSITIVE .$1441 [E5 64 ] SBC $64 ; RESULT .$1443 [85 64 ] STA $64 .$1445 [A9 00 ] LDA #$00 .$1447 [E5 65 ] SBC $65 .$1449 [85 65 ] STA $65 .$144B [A9 00 ] LDA #$00 .$144D [E5 66 ] SBC $66 .$144F [85 66 ] STA $66 .$1451 [A9 00 ] LDA #$00 .$1453 [E5 67 ] SBC $67 .$1455 [85 67 ] STA $67 .$1457 [60 ] RTS ;***************************************************************************** ;* GET THE Ř AND Ů PLOTTING INCREMENTS AND THE PIXELS-TO-PLOT COUNT * ;***************************************************************************** .$1458 [A5 0C ] LDA $0C ;GET ÁÂÓ(ÄŘ) .$145A [A4 0D ] LDY $0D .$145C [20 1A 14] JSR $141A .$145F [85 FA ] STA $FA .$1461 [84 FB ] STY $FB .$1463 [A5 10 ] LDA $10 ;GET ÁÂÓ(ÄŮ) .$1465 [A4 11 ] LDY $11 .$1467 [20 1A 14] JSR $141A .$146A [85 FC ] STA $FC .$146C [84 FD ] STY $FD .$146E [A5 FC ] LDA $FC ;COMPARE ÁÂÓ(ÄŮ) TO ÁÂÓ(ÄŘ) .$1470 [C5 FA ] CMP $FA .$1472 [A5 FD ] LDA $FD .$1474 [E5 FB ] SBC $FB .$1476 [B0 44 ] BCS $14BC ;IF ÁÂÓ(ÄŮ) >= ÁÂÓ(ÄŘ) THEN BRANCH AHEAD .$1478 [A5 FA ] LDA $FA ;SET PIXELS-TO-PLOT COUNT TO ÁÂÓ(ÄŘ) .$147A [85 12 ] STA $12 .$147C [85 50 ] STA $50 .$147E [A5 FB ] LDA $FB .$1480 [85 13 ] STA $13 .$1482 [85 51 ] STA $51 ;SET THE NUMERATOR (TOP) TO ÄŮ AND THE .$1484 [A5 FC ] LDA $FC ; DENOMINATOR (BOTTOM) TO ÁÂÓ(ÄŘ) .$1486 [85 62 ] STA $62 .$1488 [A5 FD ] LDA $FD .$148A [85 63 ] STA $63 .$148C [A5 11 ] LDA $11 ;GET THE SIGN OF ÄŮ - WILL BE THE SIGN OF DIV .$148E [20 31 14] JSR $1431 ;PERFORM THE SIGNED FRACTIONAL DIVISION .$1491 [A2 03 ] LDX #$03 ;STORE THE RESULT IN THE Ů INCREMENT VALUE .$1493 [B5 64 ] LDA $64,X .$1495 [95 0E ] STA $0E,X .$1497 [CA ] DEX .$1498 [10 F9 ] BPL $1493 .$149A [A5 0D ] LDA $0D ;GET THE Ř INCREMENT .$149C [30 0A ] BMI $14A8 .$149E [A9 00 ] LDA #$00 ;IF ÄŘ IS POSITIVE, Ř INC IS +1 .$14A0 [85 0D ] STA $0D ; (NOTE THAT ÄŘ CANNOT BE 0 HERE SO WE DON'T .$14A2 [A9 01 ] LDA #$01 ; HAVE TO WORRY ABOUT THAT CASE) .$14A4 [85 0C ] STA $0C .$14A6 [D0 06 ] BNE $14AE .$14A8 [A9 FF ] LDA #$FF ;IF ÄŘ IS NEGATIVE, Ř INC IS -1 .$14AA [85 0D ] STA $0D .$14AC [85 0C ] STA $0C .$14AE [38 ] SEC ;TAKE THE NEGATIVE OF THE NUMBER OF PIXELS .$14AF [A9 00 ] LDA #$00 ; TO PLOT AND EXIT .$14B1 [E5 12 ] SBC $12 ;É DON'T REMEMBER EXACTLY WHY É USE THE .$14B3 [85 12 ] STA $12 ; NEGATIVE; THERE IS NOT MUCH OF A SPEED .$14B5 [A9 00 ] LDA #$00 ; IMPROVEMENT. ĎH WELL, T'IS DONE. .$14B7 [E5 13 ] SBC $13 .$14B9 [85 13 ] STA $13 .$14BB [60 ] RTS .$14BC [A5 FC ] LDA $FC ;SET THE PIXELS-TO-PLOT COUNT TO ÁÂÓ(ÄŮ) .$14BE [85 12 ] STA $12 .$14C0 [85 50 ] STA $50 .$14C2 [A5 FD ] LDA $FD .$14C4 [85 13 ] STA $13 .$14C6 [85 51 ] STA $51 ;SET THE NUMERATOR (TOP) TO ÄŘ AND THE .$14C8 [A5 FA ] LDA $FA ; DENOMINATOR(BOTTOM) TO ÁÂÓ(ÄŮ) .$14CA [85 62 ] STA $62 .$14CC [A5 FB ] LDA $FB .$14CE [85 63 ] STA $63 .$14D0 [A5 0D ] LDA $0D ;GET THE SIGN OF ÄŘ - WILL BE THE SIGN OF DIV .$14D2 [20 31 14] JSR $1431 ;DO THE 32-BIT SIGNED FRACTIONAL DIVISION .$14D5 [A2 03 ] LDX #$03 ;STORE THE RESULT IN THE Ř INCREMENT .$14D7 [B5 64 ] LDA $64,X .$14D9 [95 0A ] STA $0A,X .$14DB [CA ] DEX .$14DC [10 F9 ] BPL $14D7 .$14DE [4C EA 14] JMP $14EA ;JUMP OVER THE NEXT SECTION ;------- .$14E1 [2C FF FF] BIT $FFFF ;ÔHIS SECTION CONTAINED JUNK BEFORE AND É .$14E4 [2C FF FF] BIT $FFFF ; DON'T KNOW HOW IT GOT HERE. É REPLACED .$14E7 [2C FF FF] BIT $FFFF ; IT WITH ÂÉÔS AND NOW JUMP OVER IT. ;------- .$14EA [A5 11 ] LDA $11 .$14EC [30 0A ] BMI $14F8 .$14EE [A9 00 ] LDA #$00 ;IF ÄŮ IS POSITIVE THEN Ů INC IS +1 .$14F0 [85 11 ] STA $11 ; (WE DO NOT HAVE TO WORRY ABOUT THE CASE .$14F2 [A9 01 ] LDA #$01 ; OF ÄŮ BEING ZERO SINCE THEN THE INCREMENT .$14F4 [85 10 ] STA $10 ; WOULD NOT BE IMPORTANT) .$14F6 [D0 06 ] BNE $14FE .$14F8 [A9 FF ] LDA #$FF ;IF ÄŮ IS NEGATIVE THEN Ů INC IS -1 .$14FA [85 11 ] STA $11 .$14FC [85 10 ] STA $10 .$14FE [4C AE 14] JMP $14AE ;JUMP BACK TO THE EXIT ;***************************************************************************** ;* MAIN ROUTINE: DRAW LINE OR SET PIXEL CURSOR POSITION * ;***************************************************************************** .$1501 [B0 07 ] BCS $150A ;GOTO DRAW ROUTINE IF .Ă=1 .$1503 [85 8B ] STA $8B ;STORE X AND Y PIXEL CURSOR COORDINATES .$1505 [86 8C ] STX $8C .$1507 [84 8D ] STY $8D .$1509 [60 ] RTS ;EXIT SET PIXEL CURSOR .$150A [85 04 ] STA $04 ;SAVE DRAW-TO COORDINATES .$150C [86 05 ] STX $05 .$150E [84 08 ] STY $08 .$1510 [A2 07 ] LDX #$07 ;CLEAR $0A-$0D AND $0E-$11 .$1512 [A9 00 ] LDA #$00 .$1514 [95 0A ] STA $0A,X .$1516 [CA ] DEX .$1517 [10 FB ] BPL $1514 .$1519 [38 ] SEC ;GET DX VALUE = ÄRAWÔOŘ - ĐIXELĂURSORŘ .$151A [A5 04 ] LDA $04 ; DX IS AT [$0D $0C . $0B $0A] .$151C [E5 8B ] SBC $8B .$151E [85 0C ] STA $0C .$1520 [A5 05 ] LDA $05 .$1522 [E5 8C ] SBC $8C .$1524 [85 0D ] STA $0D .$1526 [38 ] SEC ;GET DY VALUE = ÄRAWÔOŮ - ĐIXELĂURSORŮ .$1527 [A5 08 ] LDA $08 ; DY IS AT [$11 $10 . $0F $0E] .$1529 [E5 8D ] SBC $8D .$152B [85 10 ] STA $10 .$152D [A9 00 ] LDA #$00 .$152F [B0 02 ] BCS $1533 .$1531 [A9 FF ] LDA #$FF .$1533 [85 11 ] STA $11 .$1535 [20 58 14] JSR $1458 ;CALCULATE THE Ř AND Ů PLOTTING INCREMENTS .$1538 [A5 8B ] LDA $8B ;SET THE DRAWING Ř POSITION TO X+0.5 .$153A [85 04 ] STA $04 ; Ř IS AT [$05 $04 . $03 $02] .$153C [A5 8C ] LDA $8C .$153E [85 05 ] STA $05 .$1540 [A9 80 ] LDA #$80 .$1542 [85 03 ] STA $03 .$1544 [85 07 ] STA $07 .$1546 [A9 00 ] LDA #$00 .$1548 [85 02 ] STA $02 .$154A [85 06 ] STA $06 .$154C [A5 8D ] LDA $8D ;SET THE DRAWING Ů POSITION TO Y+0.5 .$154E [85 08 ] STA $08 ; Ů IS AT [$09 $08 . $07 $06] .$1550 [A9 00 ] LDA #$00 .$1552 [85 09 ] STA $09 .$1554 [A5 04 ] LDA $04 ;GET THE PIXEL Ř AND Ů COORDINATES .$1556 [A6 05 ] LDX $05 .$1558 [A4 08 ] LDY $08 .$155A [20 A8 13] JSR $13A8 ;PLOT THE PIXEL .$155D [A5 12 ] LDA $12 ;CHECK THE PIXELS-TO-PLOT COUNT FOR ZERO .$155F [05 13 ] ORA $13 .$1561 [F0 3B ] BEQ $159E ;IF NO MORE PIXELS TO PLOT, EXIT LOOP .$1563 [18 ] CLC ;ADD THE Ř INCREMENT TO THE Ř COORDINATE .$1564 [A5 02 ] LDA $02 .$1566 [65 0A ] ADC $0A .$1568 [85 02 ] STA $02 .$156A [A5 03 ] LDA $03 .$156C [65 0B ] ADC $0B .$156E [85 03 ] STA $03 .$1570 [A5 04 ] LDA $04 .$1572 [65 0C ] ADC $0C .$1574 [85 04 ] STA $04 .$1576 [A5 05 ] LDA $05 .$1578 [65 0D ] ADC $0D .$157A [85 05 ] STA $05 .$157C [18 ] CLC ;ADD THE Ů INCREMENT TO THE Ů COORDINATE .$157D [A5 06 ] LDA $06 .$157F [65 0E ] ADC $0E .$1581 [85 06 ] STA $06 .$1583 [A5 07 ] LDA $07 .$1585 [65 0F ] ADC $0F .$1587 [85 07 ] STA $07 .$1589 [A5 08 ] LDA $08 .$158B [65 10 ] ADC $10 .$158D [85 08 ] STA $08 .$158F [A5 09 ] LDA $09 .$1591 [65 11 ] ADC $11 .$1593 [85 09 ] STA $09 .$1595 [E6 12 ] INC $12 ;INCREMENT THE PIXELS TO PLOT COUNT .$1597 [D0 BB ] BNE $1554 ; NOTE THAT IT IS STORED AS THE NEGATIVE OF .$1599 [E6 13 ] INC $13 ; THE COUNT .$159B [4C 54 15] JMP $1554 ;REPEAT PLOTTING LOOP .$159E [A5 04 ] LDA $04 ;EXIT - SET THE PIXEL CURSOR POSITION TO THE .$15A0 [A6 05 ] LDX $05 ; LAST PIXEL PLOTTED ON THE LINE .$15A2 [A4 08 ] LDY $08 .$15A4 [4C 03 15] JMP $1503