Disassembly of BBC B/B+ Tube Host 2.30 Code in DFS 2.26 ======================================================= | marks code different from Tube Host 1.xx in DNFS 3.xx (DFS 1.2x/NFS 3.6x) TUBE HOST SERVICE HANDLER ========================= AEA9 C9 09 I. CMP #&09 | Is it *HELP? AEAB D0 2A P* BNE &AED7 | No, skip ahead AEAD 98 . TYA | AEAE 48 H PHA | Save string offset AEAF B1 F2 1r LDA (&F2),Y | Get character AEB1 C9 0D I. CMP #&0D | AEB3 D0 1E P. BNE &AED3 | Not , skip to exit AEB5 A9 E9 )i LDA #&E9 | OSBYTE &E9,&00,&FF AEB7 20 E5 9A e. JSR &9AE5 | Get Tube presence to Y AEBA A6 F4 &t LDX &F4 | Restore X AEBC 98 . TYA | Check Tube presence flag AEBD F0 14 p. BEQ &AED3 | No Tube hardware, skip to exit AEBF 20 77 80 w. JSR &8077 | Print inline text AEC2 0D 54 55 .TU ORA &5554 | cr,"TUBE HOST 2.30",cr AEC5 42 B EQUB &42 | AEC6 45 20 E EOR &20 | AEC8 48 H PHA | AEC9 4F 53 54 OST BBR 4,&53,&AF20 | AECC 20 32 2E 2. JSR &2E32 | AECF 33 3 EQUB &33 | AED0 30 0D 0. BMI &AEDF | AED2 EA j NOP | AED3 68 h PLA | Get string offset back AED4 A8 ( TAY | AED5 A9 09 ). LDA #&09 | Restore A AED7 C9 FE I~ CMP #&FE Service call &FE/&FF? AED9 90 5C .\ BCC &AF37 No, jump to exit AEDB D0 1B P. BNE &AEF8 Jump with service call &FF ServFE - Tube PostInit ---------------------- AEDD C0 00 @. CPY #&00 Y=0 if Tube system not present AEDF F0 56 pV BEQ &AF37 Exit with no Tube system AEE1 A2 06 ". LDX #&06 AEE3 A9 14 ). LDA #&14 AEE5 20 F4 FF t. JSR &FFF4 Explode character set AEE8 2C E0 FE ,`~ BIT &FEE0 Check Tube Register 0 status AEEB 10 FB .{ BPL &AEE8 Loop until data present AEED AD E1 FE -a~ LDA &FEE1 Fetch data from Tube Register 0 AEF0 F0 43 pC BEQ &AF35 Data=0, jump to claim call AEF2 20 EE FF n. JSR &FFEE Print the character AEF5 4C E8 AE Lh. JMP &AEE8 Loop back for another ServFF - Tube PreInit --------------------- AEF8 A9 AD )- LDA #&AD AEFA 8D 20 02 . . STA &0220 AEFD A9 06 ). LDA #&06 AEFF 8D 21 02 .!. STA &0221 Point EVNTV to &06AD AF02 A9 16 ). LDA #&16 AF04 8D 02 02 ... STA &0202 AF07 A9 00 ). LDA #&00 AF09 8D 03 02 ... STA &0203 Point BRKV to &0016 AF0C A9 8E ). LDA #&8E AF0E 8D E0 FE .`~ STA &FEE0 Enable NMI on R1, IRQ on R4, IRQ on R1 AF11 A0 00 . LDY #&00 Initialise code at &0400-&05FF AF13 B9 79 AF 9y/ LDA &AF79,Y by copying from &AF79-&B078 AF16 99 00 04 ... STA &0400,Y AF19 B9 DB AC 9[, LDA &ACDB,Y and &ACDB-&AEDA AF1C 99 00 05 ... STA &0500,Y AF1F B9 DB AD 9[- LDA &ADDB,Y AF22 99 00 06 ... STA &0600,Y AF25 88 . DEY AF26 D0 EB Pk BNE &AF13 Loop to copy code AF28 20 21 04 !. JSR &0421 Set Tube 'free' and no owner AF2B A2 41 "A LDX #&41 Initialise code at &0016-&0057 AF2D BD 38 AF =8/ LDA &AF38,X by copying from &AF38-&AF AF30 95 16 .. STA &16,X AF32 CA J DEX AF33 10 F8 .x BPL &AF2D Loop to copy code AF35 A9 00 ). LDA #&00 Claim call AF37 60 ` RTS And return Code at &AF38 copied to &0016-&0057 =================================== 0000 EQUS 18 Control block for MOS calls 0012 00 00 EQUW &0000 Pointer to Tube transfer blovk 0014 00 EQUB &00 Tube status 0015 00 EQUB &00 Tube owner BRK handler ----------- 0016 A9 FF ). LDA #&FF 0018 20 9E 06 .. JSR &069E Send &FF to R4 to interupt CoPro 001B AD E3 FE -c~ LDA &FEE3 Get ACK byte from CoPro via R2 001E A9 00 ). LDA #&00 0020 20 95 06 .. JSR &0695 Send &00 to R2 to specify ERROR 0023 A8 ( TAY Point Y to start of error block 0024 B1 FD 1} LDA (&FD),Y Get error number 0026 20 95 06 .. JSR &0695 Send via R2 0029 C8 H INY Point to next character 002A B1 FD 1} LDA (&FD),Y Get error string character 002C 20 95 06 .. JSR &0695 Send via R2 002F AA * TAX 0030 D0 F7 Pw BNE &0029 Loop until terminating &00 sent Idle startup ------------ 0032 A2 FF ". LDX #&FF 0034 9A . TXS Clear stack 0035 58 X CLI Enable IRQs Tube idle loop -------------- 0036 2C E0 FE ,`~ BIT &FEE0 Is there a character in R1? 0039 10 06 .. BPL &0041 No, check for command in R2 003B AD E1 FE -a~ LDA &FEE1 Get character from R1 003E 20 EE FF n. JSR &FFEE Send to OSWRCH output 0041 2C E2 FE ,b~ BIT &FEE2 Is there a command in R2? 0044 10 F0 .p BPL &0036 No, loop back 0046 2C E0 FE ,`~ BIT &FEE0 Check again for character in R1 0049 30 F0 0p BMI &003B Jump to catch this character 004B AE E3 FE .c~ LDX &FEE3 Get command from R2 004E 86 51 .Q STX &51 Use as index into &0500 0050 6C 00 05 l.. JMP (&0500) Jump to command routine 0053 00 80 00 00 .... EQUD &00008000 Code at &AF79-&B078 and &ACDB-&AECA copied to &0400-&06FF ========================================================= Copy language across the Tube ----------------------------- 0400 4C 84 04 L.. JMP &0484 Copy Escape state across the Tube --------------------------------- 0403 4C A7 06 L'. JMP &06A7 Tube Transfer/Claim/Release --------------------------- 0406 C9 80 I. CMP #&80 Claim/Release/Action via Tube 0408 90 2B .+ BCC &0435 If <&80, data transfer action 040A C9 C0 I@ CMP #&C0 Is it claim or release? 040C B0 1A 0. BCS &0428 &C0-&FF - jump to claim Tube 040E 09 40 .@ ORA #&40 Ensure release ID same as claim ID 0410 C5 15 Å. CMP &15 Is the the same as the claim ID? 0412 D0 20 Ð BNE &0434 No, exit. 0414 08 . PHP Save IRQ state 0415 78 x SEI Disable IRQs 0416 A9 05 ©. LDA #&05 Send &05 to R4 to interupt CoPro 0418 20 9E 06 .. JSR &069E 041B A5 15 ¥. LDA &15 Send Tube ID to notify a Tube release 041D 20 9E 06 .. JSR &069E 0420 28 ( PLP Get IRQ state back Clear Tube status and owner --------------------------- 0421 A9 80 ©. LDA #&80 0423 85 15 .. STA &15 Set Tube ID to 'unclaimed' 0425 85 14 .. STA &14 Set Tube status to 'free' 0427 60 ` RTS Claim Tube ---------- 0428 06 14 .. ASL &14 Is Tube free? 042A B0 06 °. BCS &0432 Yes, jump to claim it 042C C5 15 Å. CMP &15 Is Tube ID same as claimer? 042E F0 04 ð. BEQ &0434 Yes, exit as we already own it 0430 18 . CLC Signal 'can't claim Tube' 0431 60 ` RTS And exit 0432 85 15 .. STA &15 Store Tube ID 0434 60 ` RTS Tube data transfer ------------------ 0435 08 . PHP Save IRQ status 0436 78 x SEI Disable IRQs 0437 84 13 .. STY &13 Store pointer to control block 0439 86 12 .. STX &12 Send action code to R4 to 043B 20 9E 06 .. JSR &069E interrupt CoPro 043E AA ª TAX Save action code in X 043F A0 03 . LDY #&03 Prepare to send 4 byte control block 0441 A5 15 ¥. LDA &15 Send Tube ID via R4, interupting 0443 20 9E 06 .. JSR &069E CoPro 0446 B1 12 ±. LDA (&12),Y Get byte from Tube control block 0448 20 9E 06 .. JSR &069E Send via R4 044B 88 . DEY 044C 10 F8 .ø BPL &0446 Loop for whole block 044E A0 18 . LDY #&18 0450 8C E0 FE .àþ STY &FEE0 Disable FIFO on R3, and NMI on R3 by default 0453 BD 18 05 =.. LDA &0518,X Get Tube I/O setting according to 0456 8D E0 FE .à~ STA &FEE0 action code and set Tube 0459 4A J LSR A 045A 4A J LSR A Move b1 to Carry (b1 set = Copro->I/O) 045B 90 06 .. BCC &0463 If no pre-delay needed, jump past 045D 2C E5 FE ,å~ BIT &FEE5 Read R3 twice to delay & empty FIFO 0460 2C E5 FE ,å~ BIT &FEE5 0463 20 9E 06 .. JSR &069E Send flag via R4 to synchronise 0466 2C E6 FE ,æ~ BIT &FEE6 Check R4 status 0469 50 FB Pû BVC &0466 Loop until data has left R4 046B B0 0D 0. BCS &047A Carry still indicates direction 046D E0 04 à. CPX #&04 Is action 'execute code'? 046F D0 11 P. BNE &0482 No, jump to finish 0471 20 14 04 .. JSR &0414 Release Tube 0474 20 95 06 .. JSR &0695 Send &80 via R2 0477 4C 32 00 L2. JMP &0032 Jump to Tube Idle loop 047A 4A J LSR A Move Tube I/O setting b2 into Carry (b2 set = NMI required) 047B 90 05 .. BCC &0482 It was clear, jump to exit 047D A0 88 . LDY #&88 Set Tube I/O to NMI on R3 047F 8C E0 FE .`~ STY &FEE0 0482 28 ( PLP Restore IRQ status 0483 60 ` RTS And exit Copy language across Tube ------------------------- On entry, A=1 - enter language, CLC=Break, SEC=OSBYTE 142 A=0 - no language found at Break 0484 58 X CLI Enable IRQs 0485 B0 0A 0. BCS &0491 Branch if selected with *fx142 0487 D0 03 P. BNE &048C A<>0, jump to enter language 0489 4C 9C 05 L.. JMP &059C A=0, jump to enter Tube Idle loop Language entered at BREAK ------------------------- 048C AE 8D 02 ... LDX &028D | Get last break type 048F F0 E0 p` BEQ &0471 If Soft Break, release Tube, send &80 via R2 and enter Idle loop The current language is not copied across the Tube on soft Break, only on Power-On Break and Hard Break, or when entered explicitly with OSBYTE 142. Language entered with OSBYTE 142, or on Hard Break -------------------------------------------------- 0491 A9 FF ). LDA #&FF 0493 20 06 04 .. JSR &0406 Claim Tube with ID=&3F 0496 90 F9 .y BCC &0491 Loop until Tube available 0498 20 CE 04 N. JSR &04CE Find address to copy language to Send language ROM via Tube 256 bytes at a time ---------------------------------------------- 049B 08 . PHP | Save IRQ status 049C 78 x SEI | Disable IRQs 049D A9 07 ). LDA #&07 Start I/O->CoPro transfer 256 bytes 049F 20 C7 04 G. JSR &04C7 Use Tube address at &53-&56 04A2 A0 00 . LDY #&00 04A4 84 00 .. STY &00 Start copying from &8000 04A6 B1 00 1. LDA (&00),Y Get byte from ROM 04A8 8D E5 FE .e~ STA &FEE5 Send to CoPro via R3 04AB EA j NOP Delay for a while 04AC EA j NOP 04AD EA j NOP 04AE C8 H INY 04AF D0 F5 Pu BNE &04A6 Loop for 256 bytes 04B1 28 ( PLP | Restore IRQs 04B2 E6 54 fT INC &54 Update Tube address 04B4 D0 06 P. BNE &04BC 04B6 E6 55 fU INC &55 04B8 D0 02 P. BNE &04BC 04BA E6 56 fV INC &56 04BC E6 01 f. INC &01 Update source address 04BE 24 01 $. BIT &01 Check b6 of source high byte 04C0 50 D9 PY BVC &049B Loop until source=&C000 04C2 20 CE 04 N. JSR &04CE Find start address language copied to 04C5 A9 04 ). LDA #&04 Execute code in CoPro, finished by sending &80 to Copro in R2 Start a Tube transfer with address block at &0053 ------------------------------------------------- 04C7 A0 00 . LDY #&00 04C9 A2 53 "S LDX #&53 Point to Tube control block 04CB 4C 06 04 L.. JMP &0406 Jump to do a data transfer Set Tube address to destination to copy language to --------------------------------------------------- Also sets source address at &00/&01 to &80xx 04CE A9 80 ). LDA #&80 04D0 85 54 .T STA &54 Set Tube address to &xxxx80xx 04D2 85 01 .. STA &01 Set source address to &80xx 04D4 A9 20 ) LDA #&20 04D6 2D 06 80 -.. AND &8006 Check relocation bit in ROM type 04D9 A8 ( TAY If no relocation address, A=0, Y=0 04DA 84 53 .S STY &53 Set Tube address to &xxxx8000 04DC F0 19 p. BEQ &04F7 Jump forward with no relocation 04DE AE 07 80 ... LDX &8007 Get offset to ROM copyright 04E1 E8 h INX 04E2 BD 00 80 =.. LDA &8000,X Skip past copyright message 04E5 D0 FA Pz BNE &04E1 Loop until terminating zero byte 04E7 BD 01 80 =.. LDA &8001,X Get relocation address from after 04EA 85 53 .S STA &53 copyright message 04EC BD 02 80 =.. LDA &8002,X 04EF 85 54 .T STA &54 04F1 BC 03 80 <.. LDY &8003,X Get two high bytes to Y and A 04F4 BD 04 80 =.. LDA &8004,X Set Tube address high bytes --------------------------- 04F7 85 56 .V STA &56 Set Tube address high bytes 04F9 84 55 .U STY &55 04FB 60 ` RTS Spare bytes ----------- 04FC 0A . ASL A | 04FD 53 S EQUB &53 | 04FE 52 41 RA EOR (&41) | Tube R2 command entry block --------------------------- 0500 37 05 7. EQUW &0537 RDCH 0502 96 05 .. EQUW &0596 CLI 0504 F2 05 ò. EQUW &05F2 BYTELO 0506 07 06 .. EQUW &0607 BYTEHI 0508 27 06 '. EQUW &0627 WORD 050A 68 06 h. EQUW &0668 WORD0 050C 5E 05 ^. EQUW &055E ARGS 050E 2D 05 -. EQUW &052D BGET 0510 20 05 . EQUW &0520 BPUT 0512 42 05 B. EQUW &0542 FIND 0514 A9 05 ©. EQUW &05A9 FILE 0516 D1 05 Ñ. EQUW &05D1 GBPB Tube data transfer flags ------------------------ 0518 86 . EQUB &86 CoPro->I/O bytes 0519 88 . EQUB &88 I/O->CoPro bytes 051A 96 . EQUB &96 CoPro->I/O words 051B 98 EQUB &98 I/O->CoPro words 051C 18 . EQUB &18 Execute in CoPro 051D 18 . EQUB &18 Reserved 051E 82 . EQUB &82 CoPro->I/O 256 bytes 051F 18 . EQUB &18 I/O->CoPro 256 bytes BPUT ---- 0520 20 C5 06 Å. JSR &06C5 Wait for a byte in R2 0523 A8 ¨ TAY Pass to Y as file handle 0524 20 C5 06 Å. JSR &06C5 Wait for a byte in R2 0527 20 D4 FF Ô. JSR OSBPUT Write byte to file 052A 4C 9C 05 L.. JMP &059C Send &7F ack byte via R2 and return to idle loop BGET ---- 052D 20 C5 06 Å. JSR &06C5 Wait for a byte in R2 0530 A8 ¨ TAY Pass to Y as file handle 0531 20 D7 FF ×. JSR OSBGET Fetch a byte from file 0534 4C 3A 05 L:. JMP &053A Jump to send Carry and A RDCH ---- 0537 20 E0 FF à. JSR OSRDCH Wait for a character 053A 6A j ROR A Move carry to b7 053B 20 95 06 .. JSR &0695 Send via R2 053E 2A * ROL A Move A back 053F 4C 9E 05 L.. JMP &059E Send via R2 and return to idle loop FIND ---- 0542 20 C5 06 Å. JSR &06C5 Wait for a byte in R2 0545 F0 0B p. BEQ &0552 Zero - jump to do CLOSE 0547 48 H PHA Save OPEN action 0548 20 82 05 .. JSR &0582 Get a string via R2 054B 68 h PLA Get OPEN function back 054C 20 CE FF Î. JSR OSFIND Do the OPEN 054F 4C 9E 05 L.. JMP &059E Send handle via R2 and go to idle loop CLOSE ----- 0552 20 C5 06 Å. JSR &06C5 Wait for a byte in R2 0555 A8 ¨ TAY Pass to Y as handle 0556 A9 00 ©. LDA #&00 Set A=0 for CLOSE 0558 20 CE FF Î. JSR OSFIND Do the CLOSE 055B 4C 9C 05 L.. JMP &059C Send &7F ack and jump to idle loop ARGS ---- 055E 20 C5 06 Å. JSR &06C5 Wait for a byte in R2 0561 A8 ¨ TAY Pass to Y as handle 0562 A2 04 ". LDX #&04 Fetch four bytes for control block 0564 20 C5 06 Å. JSR &06C5 Wait for a byte in R2 0567 95 FF .. STA &FF,X Store in &03,&02,&01,&00 0569 CA Ê DEX 056A D0 F8 Pù BNE &0564 Loop for four bytes, X now &00 056C 20 C5 06 Å. JSR &06C5 Wait for ARGS function via R2 056F 20 DA FF Ú. JSR OSARGS Do the OSARGS action 0572 20 95 06 .. JSR &0695 Send A back via R2 0575 A2 03 ". LDX #&03 Send four bytes from control block 0577 B5 00 µ. LDA &00,X Fetch from &03,&02,&01,&00 0579 20 95 06 .. JSR &0695 Send via R2 057C CA Ê DEX 057D 10 F8 .ù BPL &0577 Loop for four bytes 057F 4C 36 00 L6. JMP &0036 Jump to Tube idle loop Read a string via R2 into string buffer at &0700 ------------------------------------------------ 0582 A2 00 ". LDX #&00 Set X to point to &xx00 0584 A0 00 . LDY #&00 0586 20 C5 06 Å. JSR &06C5 Wait for a byte via R2 0589 99 00 07 ... STA &0700,Y Store in string buffer 058C C8 È INY Move to next byte 058D F0 04 p. BEQ &0593 Buffer full, end loop 058F C9 0D I. CMP #&0D Was last char ? 0591 D0 F3 Pó BNE &0586 Loop until received 0593 A0 07 . LDY #&07 Return XY pointing to &0700 0595 60 ` RTS CLI --- 0596 20 82 05 .. JSR &0582 Read string to &0700 0599 20 F7 FF ÷. JSR OSCLI Execute the command If the command returns here, the CoPro will get &7F as an acknowledgement. The CoPro also gets sent a &7F byte if there is no language available on Break. If calling OSCLI results in code being run in the CoPro or a language being copied over and entered, the CoPro will get an &80 acknowledgement elsewhere. Send &7F acknowledgement byte via R2 and return to idle loop ------------------------------------------------------------ 059C A9 7F ©. LDA #&7F Send &7F to CoPro Send byte in A via R2 and return to Tube idle loop -------------------------------------------------- 059E 2C E2 FE ,â~ BIT &FEE2 Check R2 status 05A1 50 FB Pû BVC &059E Loop until port free 05A3 8D E3 FE .ã~ STA &FEE3 Send byte in A 05A6 4C 36 00 L6. JMP &0036 Jump to Tube idle loop FILE ---- 05A9 A2 10 ". LDX #&10 Loop for 16-byte control block 05AB 20 C5 06 Å. JSR &06C5 Wait for a byte in R2 05AE 95 01 .. STA &01,X Store in control block 05B0 CA Ê DEX 05B1 D0 F8 Pù BNE &05AB Loop to store high->low 05B3 20 82 05 .. JSR &0582 Read string to &0700 05B6 86 00 .. STX &00 Point control block to string 05B8 84 01 .. STY &01 05BA A0 00 . LDY #&00 Point XY to &0000 05BC 20 C5 06 Å. JSR &06C5 Wait for action byte via R2 05BF 20 DD FF Ý. JSR OSFILE Do the OSFILE call During the OSFILE call the Tube system may be called to do a data transfer 05C2 20 95 06 .. JSR &0695 Send result back via R2 05C5 A2 10 ¢. LDX #&10 Send 16-byte control block back 05C7 B5 01 µ. LDA &01,X Get byte from control block 05C9 20 95 06 .. JSR &0695 Send via R2 05CC CA Ê DEX 05CD D0 F8 Ðø BNE &05C7 Loop to send high->low 05CF F0 D5 ðÕ BEQ &05A6 Jump to Tube idle loop GBPB ---- 05D1 A2 0D ¢. LDX #&0D Loop for 13-byte control block 05D3 20 C5 06 Å. JSR &06C5 Wait for a byte in R2 05D6 95 FF .. STA &FF,X Store in control block 05D8 CA Ê DEX 05D9 D0 F8 Ðø BNE &05D3 Loop to store high->low, X now &00 05DB 20 C5 06 Å. JSR &06C5 Wait for action byte via R2 05DE A0 00 . LDY #&00 Set XY to point to &0000 05E0 20 D1 FF Ñ. JSR OSGBPB Do the OSGBPB call During the OSGBPB call the Tube system may be called to do a data transfer 05E3 48 H PHA Save the result 05E4 A2 0C ¢. LDX #&0C Loop for 13-byte control block 05E6 B5 00 µ. LDA &00,X Get byte from control block 05E8 20 95 06 .. JSR &0695 Send via R2 05EB CA Ê DEX 05EC 10 F8 .ø BPL &05E6 Loop to send high->low 05EE 68 h PLA Get result byte byte 05EF 4C 3A 05 L:. JMP &053A Jump to send Carry and A, then return to Tube idle loop BYTELO - OSBYTEs &00-&7F ------------------------ 05F2 20 C5 06 Å. JSR &06C5 Wait for a byte in R2 05F5 AA ª TAX Pass this to X 05F6 20 C5 06 Å. JSR &06C5 Wait for byte in R2 to use a A 05F9 20 F4 FF ô. JSR OSBYTE Do the OSBYTE call Send byte in X via R2 and jump to Tube idle loop ------------------------------------------------ 05FC 2C E2 FE ,âþ BIT &FEE2 Check R2 status 05FF 50 FB Pû BVC &05FC Loop until port free 0601 8E E3 FE .ãþ STX &FEE3 Send X via R2 0604 4C 36 00 L6. JMP &0036 Return to Tube idle loop BYTEHI - OSBYTE &80-&FF ----------------------- 0607 20 C5 06 Å. JSR &06C5 Wait for a byte in R2 060A AA ª TAX Pass this to X 060B 20 C5 06 Å. JSR &06C5 Wait for a byte in R2 060E A8 ¨ TAY Pass this to Y 060F 20 C5 06 Å. JSR &06C5 Wait for byte in R2 to use as A 0612 20 F4 FF ô. JSR OSBYTE Do the OSBYTE call If the OSBYTE results in code being executed - ie, OSBYTE 142, then the call will not be returned here, and the CoPro will be sent an &80 ack byte. 0615 49 9D I. EOR #&9D Was if OSBYTE &9D - Fast BPUT? 0617 F0 EB ðë BEQ &0604 If so, jump stright back to idle loop 0619 6A j ROR A Move Carry into b7 of A 061A 20 95 06 .. JSR &0695 Send via R2 Send bytes in Y, X via R2, then jump to Tube idle loop ------------------------------------------------------ 061D 2C E2 FE ,âþ BIT &FEE2 Check R2 status 0620 50 FB Pû BVC &061D Loop until port free 0622 8C E3 FE .ãþ STY &FEE3 Send byte in Y 0625 70 D5 pÕ BVS &05FC Jump to send X and jump to idle loop WORD ---- 0627 20 C5 06 Å. JSR &06C5 Wait for action byte in R2 062A A8 ¨ TAY Save in Y 062B 2C E2 FE ,âþ BIT &FEE2 Check R2 status 062E 10 FB .û BPL &062B Loop until data present 0630 AE E3 FE ®ãþ LDX &FEE3 Get X from R2 - number of bytes inward 0633 CA Ê DEX See if no bytes to read. Note: this 0634 30 0F 0. BMI &0645 treats &81-&FF as zero as well 0636 2C E2 FE ,âþ BIT &FEE2 Check R2 status 0639 10 FB .û BPL &0636 Loop until data present 063B AD E3 FE ãþ LDA &FEE3 Get byte from R2 063E 9D 28 01 .(. STA &0128,X Store in control block 0641 CA Ê DEX 0642 10 F2 .ò BPL &0636 Loop to read high->low 0644 98 . TYA Get function byte to A This builds the OSWORD control block in &0128 up towards &01FF, allowing a maximum control block of almost 216 bytes before it crashes into the stack. However, the protocol treats a control block length of &81-&FF as zero, so the maximum size control block will be &0128-&01A7. 0645 A2 28 ¢( LDX #&28 Point XY to control block at &0128 0647 A0 01 . LDY #&01 0649 20 F1 FF ñ. JSR OSWORD Do the OSWORD call 064C 2C E2 FE ,âþ BIT &FEE2 Check R2 status 064F 10 FB .û BPL &064C Loop until data present 0651 AE E3 FE ®ãþ LDX &FEE3 Get output control block size to X 0654 CA Ê DEX See if no bytes to return - again, 0655 30 0E 0. BMI &0665 treating &81-&FF as zero. 0657 BC 28 01 ¼(. LDY &0128,X Get byte from control block 065A 2C E2 FE ,âþ BIT &FEE2 Check R2 status 065D 50 FB Pû BVC &065A Loop until port free 065F 8C E3 FE .ãþ STY &FEE3 Send byte to R2 0662 CA Ê DEX 0663 10 F2 .ò BPL &0657 Loop to send bytes high->low 0665 4C 36 00 L6. JMP &0036 Return to Tube idle loop WORD0 - Read a line ------------------- 0668 A2 04 ¢. LDX #&04 Fetch five bytes into control block 066A 20 C5 06 Å. JSR &06C5 Wait for a byte via R2 066D 95 00 .. STA &00,X Store in control block 066F CA Ê DEX 0670 10 F8 .ø BPL &066A Loop to get five bytes high->low 0672 E8 è INX Increment X back to &00 0673 A0 00 . LDY #&00 Point XY to control block at &0000 0675 8A . TXA Set A=0 to read a line 0676 20 F1 FF ñ. JSR OSWORD Call OSWORD to read the line This call assumes that the CoPro client code has sent the bottom two bytes as &00,&07 so that the OSWORD call will read the text line to &0700. There is enough space to make the code do LDA #7:STA &01:TXA:TAY:STY &00:JSR OSWORD. 0679 90 05 .. BCC &0680 Jump if no Escape 067B A9 FF ©. LDA #&FF Send &FF via R2 to indicate Escape 067D 4C 9E 05 L.. JMP &059E and return to Tube idle loop 0680 A2 00 ¢. LDX #&00 Point to start of string buffer 0682 A9 7F ©. LDA #&7F 0684 20 95 06 .. JSR &0695 Send &7F via R2 to indicate no Escape 0687 BD 00 07 ½.. LDA &0700,X Get byte from string buffer 068A 20 95 06 .. JSR &0695 Send byte via R2 068D E8 è INX Move to next byte 068E C9 0D É. CMP #&0D 0690 D0 F5 Ðõ BNE &0687 Loop until sent 0692 4C 36 00 L6. JMP &0036 Jump to Tube idle loop Send byte in A via R2 --------------------- 0695 2C E2 FE ,âþ BIT &FEE2 Check R2 status 0698 50 FB Pû BVC &0695 Loop until port free 069A 8D E3 FE .ãþ STA &FEE3 Send byte 069D 60 ` RTS Send byte in A via R4 --------------------- 069E 2C E6 FE ,æþ BIT &FEE6 Check R4 status 06A1 50 FB Pû BVC &069E Loop until port free 06A3 8D E7 FE .çþ STA &FEE7 Send byte 06A6 60 ` RTS Copy Escape state across Tube ----------------------------- 06A7 A5 FF ¥. LDA &FF Get Escape state 06A9 38 8 SEC 06AA 6A j ROR A Rotate escape to b6 and set b7 06AB 30 0F 0. BMI &06BC Interupt client with byte send via R1 Send event across Tube ---------------------- 06AD 48 H PHA Save A 06AE A9 00 ©. LDA #&00 06B0 20 BC 06 ¼. JSR &06BC Send &00 via R1, generating client IRQ After being interupted with the first byte, above, the client usually disables IRQs and reads the following bytes directly from the Tube registers. 06B3 98 . TYA 06B4 20 BC 06 ¼. JSR &06BC Send Y via R1 06B7 8A . TXA 06B8 20 BC 06 ¼. JSR &06BC Send X via R1 06BB 68 h PLA Get A back and send via R1 Send byte in A via R1 --------------------- 06BC 2C E0 FE ,àþ BIT &FEE0 Check R1 status 06BF 50 FB Pû BVC &06BC Loop until port free 06C1 8D E1 FE .áþ STA &FEE1 Send byte 06C4 60 ` RTS Wait for data via R2 -------------------- 06C5 2C E2 FE ,âþ BIT &FEE2 Check R2 status 06C8 10 FB .û BPL &06C5 Loop until data present 06CA AD E3 FE ãþ LDA &FEE3 Get byte 06CD 60 ` RTS Unused space ------------ 06CE-06FF String buffer ------------- 0700 EQUS 256 String buffer History ------- 28-Oct-2006 Initial disassembly and commentary by JGH