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Maciej Witkowiak
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Feb 22, 2024
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| Development diary (Maciej 'YTM/Elysium' Witkowiak) | ||
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| [20240211] | ||
| In April 2022, shortly after receiving universal EEPROM programmer TL866II+ I wanted to quickly make The Servant more useful on a C128 with SD2IEC. | ||
| All I wanted was to be able to quickly navigate folders and disk images in the directory listing (option '4'). | ||
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| The Servant only knows about 1581 (and maybe CMD?) subdirectories marked as 'CBM', while SD2IEC returns 'DIR'. | ||
| I started disassembly, but 32K of this dense code, with encrypted strings was just not worth the effort. | ||
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| Today I went back to this problem, this time trying to trace where keyboard is read and what happens next. It seems I figured this out. | ||
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| 8d04 cmp #$2f '/' | ||
| beq $8ca8 | ||
| 8d1c cmp #$0d '<RETURN>' | ||
| beq $8d54 | ||
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| 8d88 - CMP #$50 'P' -> PRG, load and run | ||
| CMP #$43 'C' -> CBM, change 'D'IR? | ||
| yes -> $8d90 | ||
| saves filename in buffer at $0203, changes first characters to be '/:' and calls SETNAM $FFBD with '/:<name>' to enter folder | ||
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| .C:8ca8 20 7B 81 JSR $817B -> close all files/channels ($98DA) + smth + set D0/D1<-0 | ||
| .C:8cab 20 E5 99 JSR $99E5 -> (below) | ||
| .C:8cae 20 98 A7 JSR $A798 -> ? | ||
| .C:8cb1 4C C3 8B JMP $8BC3 -> ? | ||
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| .C:99e5 20 B1 9F JSR $9FB1 -> detect drivetype, memory-read | ||
| .C:99e8 C0 06 CPY #$06 -> 6==1581? | ||
| .C:99ea D0 08 BNE $99F4 -> not, do nothing | ||
| .C:99ec A9 FE LDA #$FE -> $FE==special function, send 'I0' via 9844 | ||
| .C:99ee 20 29 98 JSR $9829 -> send disk command $FE or A/X/Y parameters for SETNAME or $FF (do... what?) | ||
| .C:99f1 20 DA 98 JSR $98DA -> close all files/channels | ||
| .C:99f4 60 RTS | ||
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| .C:9829 C9 FE CMP #$FE | ||
| .C:982b F0 17 BEQ $9844 | ||
| .C:982d C9 FF CMP #$FF | ||
| .C:982f D0 19 BNE $984A | ||
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| .C:9844 A9 02 LDA #$02 | ||
| .C:9846 A2 68 LDX #$68 | ||
| .C:9848 A0 98 LDY #$98 | ||
| .C:984a 20 BD FF JSR $FFBD | ||
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| <RETURN> - Enter directory | ||
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| Check for filetype - simply use 2nd letter, not first: | ||
| PSUDRCD | ||
| RESEEBI | ||
| GQRLLMR | ||
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| 'R' -> PRG, run | ||
| 'B' -> CBM, call '/:<name>' | ||
| 'I' -> DIR, call 'CD<name>' | ||
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| / - go to root | ||
| on 1581: I0 | ||
| check for drive, read channel after 'UI' and wait for 'SD2IEC'? worth it? | ||
| or just send 'CD<-' and ignore the error | ||
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| [20240212] | ||
| Following skeleton from patching 1571-32K ROM I used KickAss to patch binaries. This was very quick and easy. | ||
| In VICE it's more tricky, the result has no load address and must be loaded from machine monitor with 2 byte offset. | ||
| This is not tested yet, it's too late today. I just wonder if it works. It would be nice to have something that was right on the first attempt. | ||
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| [20240213] | ||
| Flashed a new rom and it worked on the first try. That's a completely new level of convenience. | ||
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| [20240214] | ||
| Figured out QBB code. Not many know about QBB - it was a cartridge that mapped banked 16K or RAM in $8000-$BFFF space. There were several versions, even up to 256K but there is no information how these extra banks were controlled. VICE emulates DQBB (double quick brown box), but on C128 it always switches to C64 mode. Real one had a switch to enable/disable 128 mode (probably on /EXROM or /GAME). | ||
| Servant can use only 4 banks = 64K. $DE00 is a control register. Writing to that RAM corrupts underlying system RAM so Servant already switched to bank 1 (or 3 on expanded C128) ($CA into $FF00). | ||
| Let's just use bank 3 (1 on unexpanded in place of QBB). To get access to RAM we can just remap stack. But we also need to turn off memory sharing in lower half - shared memory always covers remapped page0/page1. | ||
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| Servant flags: $0279 - $00 - no QBB, $FF - QBB exists; $0277/78 last available address in QBB ($3FFF, $7FFF, $BFFF or $FFFF - 4 banks) | ||
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| .C:8231 - copy $22 bytes from $87A7-$87C8 (inclusive) to $0237 - the code to read/write into QBB lives there in $0237; $CE/CF are temp registers | ||
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| 8332 read from C3/C4 (+increment C3/C4) -> copy C3/C4 to X/Y, set C=1 -> C=1 setup QBB register+address in $CE/$CF, X/A -> read from CE/CF | ||
| 833F write into C1/C2 (+increment C1/C2) -> copy C1/C2 to X/Y, set C=0 -> C=0 setup QBB register+address in $CE/$CF, X/A -> write to CE/CF | ||
| 834A common part to setup address in CE/CF, value for control register, push $FF00 and jump into $0237 to continue. $0237 returns with C=0 always. | ||
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| ; common calculation part | ||
| .C:834a 08 PHP | ||
| .C:834b CC 78 02 CPY $0278 | ||
| .C:834e 90 05 BCC $8355 | ||
| .C:8350 EC 77 02 CPX $0277 | ||
| .C:8353 B0 27 BCS $837C ; requested address from C1/C2 or C3/C4 out of range | ||
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| .C:8355 48 PHA ; keep value to write | ||
| .C:8356 86 CE STX $CE ; lower address byte | ||
| .C:8358 98 TYA ; page address, convert to range $0000-$3FFF, shift to $8000-$BFFF, put into $CF | ||
| .C:8359 2A ROL A ; page address, convert to bank number for $DE00 control register | ||
| .C:835a 2A ROL A | ||
| .C:835b 2A ROL A | ||
| .C:835c 29 03 AND #$03 | ||
| .C:835e 85 CF STA $CF | ||
| .C:8360 A9 03 LDA #$03 | ||
| .C:8362 38 SEC | ||
| .C:8363 E5 CF SBC $CF | ||
| .C:8365 09 38 ORA #$38 | ||
| .C:8367 AA TAX | ||
| .C:8368 98 TYA | ||
| .C:8369 09 80 ORA #$80 | ||
| .C:836b 29 BF AND #$BF | ||
| .C:836d 85 CF STA $CF | ||
| .C:836f 68 PLA ; restore value to write | ||
| .C:8370 28 PLP ; restore C flag | ||
| .C:8371 A8 TAY | ||
| .C:8372 AD 00 FF LDA $FF00 | ||
| .C:8375 48 PHA | ||
| .C:8376 98 TYA | ||
| .C:8377 A0 00 LDY #$00 | ||
| .C:8379 4C 37 02 JMP $0237 | ||
| .C:837c 68 PLA ; fix stack, we don't need C flag anymore | ||
| .C:837d 60 RTS | ||
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| This goes into $0237 | ||
| .C:87a7 8E 00 DE STX $DE00 | ||
| .C:87aa A2 CA LDX #$CA | ||
| .C:87ac 8E 00 FF STX $FF00 | ||
| .C:87af AE 30 D0 LDX $D030 | ||
| .C:87b2 8C 30 D0 STY $D030 | ||
| .C:87b5 B0 02 BCS $87B9 | ||
| .C:87b7 91 CE STA ($CE),Y | ||
| .C:87b9 B1 CE LDA ($CE),Y | ||
| .C:87bb 8E 30 D0 STX $D030 | ||
| .C:87be 8C 00 DE STY $DE00 | ||
| .C:87c1 AA TAX | ||
| .C:87c2 68 PLA | ||
| .C:87c3 8D 00 FF STA $FF00 | ||
| .C:87c6 8A TXA | ||
| .C:87c7 18 CLC | ||
| .C:87c8 60 RTS | ||
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| [20240215] | ||
| THERE WAS A BUG IN QBB CODE. Who would have thought: | ||
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| .C:8f6a 20 32 83 JSR $8332 | ||
| .C:8f6d B0 73 BCS $8FE2 | ||
| .C:8f6f A6 37 LDX $37 | ||
| .C:8f71 A0 00 LDY #$00 | ||
| .C:8f73 20 77 FF JSR $FF77 | ||
| .C:8f76 E6 AE INC $AE | ||
| .C:8f78 D0 02 BNE $8F7C | ||
| .C:8f7a E6 AF INC $AF | ||
| .C:8f7c A5 C4 LDA $C4 | ||
| .C:8f7e C5 C0 CMP $C0 | ||
| .C:8f80 90 E8 BCC $8F6A | ||
| .C:8f82 A5 C3 LDA $C3 | ||
| .C:8f84 C5 BF CMP $BF | ||
| .C:8f86 90 E2 BCC $8F6A | ||
| .C:8f88 20 BB 83 JSR $83BB | ||
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| It should compare $C3/C4 (end address within QBB) with $C1/$C2 (current pointer within QBB for read), not $BF/$C0. | ||
| Because of the bug no more than one page was ever copied back. | ||
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| [20240215 (2)] | ||
| Now a new branch to GO64 into bank2 if after 9 (or SHIFT+9), the confirmation was pressed with C= key. | ||
| C- flag is checked and saved in $05 (0,<>0) and $06 (1 or 2). | ||
| It was really hard to squeeze all the patches. Had to remove option to reset prefs (SHIFT+'+'). | ||
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| Main menu loop starts at $82c3 | ||
| List of option keys in $885b for $16 items, check and get item number in Y | ||
| $8304-$830d take from table at $8871 vector of the procedure | ||
| For '9' it's Y=$0D -> $84C4 | ||
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| .C:84c4 A5 D3 LDA $D3 ; shift == 1 | ||
| .C:84c6 38 SEC | ||
| .C:84c7 6A ROR A ; | ||
| .C:84c8 6A ROR A ; gdy shift to $C0, gdy nic to $40; gdy control to $40 | ||
| .C:84c9 85 9D STA $9D | ||
| .C:84cb 20 66 81 JSR $8166 | ||
| .C:84ce 4C 3B 85 JMP $853B ; GO64, LOAD(*),64 (3), RUN64 z QBB (A) ; but not (2) nor DIR(4)+RUN64(F7) | ||
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| .C:8166 A9 BC LDA #$BC ; ask for confirmation | ||
| .C:8168 20 D4 89 JSR $89D4 | ||
| .C:816b 20 83 81 JSR $8183 | ||
| .C:816e 20 FA A2 JSR $A2FA | ||
| .C:8171 C9 0D CMP #$0D ; allow for C=+RETURN ($8D) here | ||
| .C:8173 D0 15 BNE $818A | ||
| .C:8175 AD A1 02 LDA $02A1 | ||
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| 00d3 Key shift flag: | ||
| 0 No shift | ||
| 1 Shift | ||
| 2 C= | ||
| 4 Control | ||
| 8 Alt | ||
| 15 Caps Lock | ||
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| 88df - here C64 mode (9)GO64 and load"*",64 (3) and RUN64 from QBB (A-Z) start | ||
| .C:853b 20 10 A6 JSR $A610 | ||
| .C:853e A9 00 LDA #$00 | ||
| .C:8540 85 24 STA $24 | ||
| .C:8542 A9 04 LDA #$04 | ||
| .C:8544 85 25 STA $25 | ||
| .C:8546 A9 24 LDA #$24 | ||
| .C:8548 8D B9 02 STA $02B9 | ||
| .C:854b A0 00 LDY #$00 | ||
| .C:854d B9 DF 88 LDA $88DF,Y | ||
| .C:8550 A2 01 LDX #$01 | ||
| .C:8552 20 77 FF JSR $FF77 | ||
| .C:8555 C8 INY | ||
| .C:8556 D0 F5 BNE $854D | ||
| .C:8558 8C 16 D0 STY $D016 | ||
| .C:855b A6 24 LDX $24 | ||
| .C:855d A4 25 LDY $25 | ||
| .C:855f A9 01 LDA #$01 ;; <- bank number ? | ||
| .C:8561 4C F1 85 JMP $85F1 | ||
| ;; | ||
| .C:85f1 8D D5 03 STA $03D5 | ||
| .C:85f4 85 02 STA $02 | ||
| .C:85f6 84 03 STY $03 | ||
| .C:85f8 86 04 STX $04 | ||
| .C:85fa A9 00 LDA #$00 | ||
| .C:85fc 85 05 STA $05 | ||
| .C:85fe 85 F7 STA $F7 | ||
| .C:8600 A9 40 LDA #$40 | ||
| .C:8602 48 PHA | ||
| .C:8603 A9 02 LDA #$02 | ||
| .C:8605 48 PHA | ||
| .C:8606 4C 6E FF JMP $FF6E ;; jsr far | ||
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| ; this goes to $0400 in target bank | ||
| .C:88df A9 7E LDA #$7E ; 01=bank 1; 11=ram 11=ram; 1=ram; 0=i/o | ||
| .C:88e1 8D 00 FF STA $FF00 | ||
| .C:88e4 A5 AE LDA $AE | ||
| .C:88e6 8D E8 07 STA $07E8 | ||
| .C:88e9 A5 AF LDA $AF | ||
| .C:88eb 8D E9 07 STA $07E9 | ||
| .C:88ee A5 BA LDA $BA | ||
| .C:88f0 8D EA 07 STA $07EA | ||
| .. | ||
| .C:8911 A9 40 LDA #$40 ; 01=bank 1; 10=bank 2 ; offset $33 | ||
| .C:8913 8D 06 D5 STA $D506 | ||
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| ; need to recover more space | ||
| ; handler for + key | ||
| .C:83f1 A5 D3 LDA $D3 | ||
| .C:83f3 4A LSR A | ||
| .C:83f4 B0 4A BCS $8440 ; set_Default_colors | ||
| .C:83f6 4A LSR A | ||
| .C:83f7 4A LSR A | ||
| .C:83f8 B0 59 BCS $8453 | ||
| .C:83fa 20 00 84 JSR $8400 ; setup_screen_and_key | ||
| .C:83fd 4C 8D 81 JMP $818D | ||
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| set_Default_colors | ||
| .C:8440 A2 0D LDX #$0D | ||
| .C:8442 A0 0B LDY #$0B | ||
| .C:8444 A9 00 LDA #$00 | ||
| .C:8446 20 26 84 JSR $8426 | ||
| .C:8449 A2 0D LDX #$0D | ||
| .C:844b A0 07 LDY #$07 | ||
| .C:844d 20 31 84 JSR $8431 | ||
| .C:8450 4C 8D 81 JMP $818D | ||
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| ; 8453 - CTRL+'+' save servant.mod | ||
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| [20240219] | ||
| Final touches - bump version to 4.85 to make it distinct. Patch default colors to almost stock C128 Kernal in 40 columns and white on blue in 80 columns. | ||
| Changed default Servant key from SHIFT+RUN/STOP into HELP. | ||
| This is complete. Now it needs a proper readme.md and release with build via github actions (working template for KickAss is with 1571-RAM32K ROM) | ||
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| [20240221] | ||
| Published on github | ||
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| ------------------------------------------------- | ||
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| --> to manual | ||
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| Bumped version number to 4.85 | ||
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| SHIFT+'+' option to reset to default prefs removed | ||
| CTRL+'+' option to save SERVANT.MOD to burn as EPROM removed | ||
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| 4 | ||
| then <RETURN> on CBM (1581) or DIR (sd2iec) will enter that directory | ||
| then / on 1581 goes to root dir, on sd2iec to parent dir (level up - out of disk image or to parent directory) | ||
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| ^ to format QBB in bank 3 (or 1 on unexpanded C128), then use F1/F3 to load data into there. It's not much but can cache something in bank 1. | ||
| Note that bank1 will be destroyed if you go to C64 mode via Servant's option on key 9. | ||
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| 9 or SHIFT+9 | ||
| On the confirmation message press RETURN to run C64 mode in bank1 or C=+RETURN to run in bank 2 (or 0 on unexpanded C128) | ||
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| SD2IEC should show disk images as DIRs, so issue XI1 or XI2 and store as default. In JiffyDos this needs quotes: | ||
| @"XI1",9 | ||
| Write defaults to EEPROM | ||
| @"XW",9 | ||
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| SD2IEC manuals: | ||
| https://c64os.com/post/sd2iecdocumentation | ||
| https://www.sd2iec.de/gitweb/?p=sd2iec.git;a=blob;f=README;hb=HEAD | ||
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| HINTS: | ||
| Modifiers to choose device for boot/run/run64/directory/DOS command ('@') | ||
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| dev 9: SHIFT | ||
| dev10: C= | ||
| dev11: CTRL | ||
| dev12: ALT | ||
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| DOS commands reminder: | ||
| <SHIFT>+<RETURN> recall last command | ||
| UI warm reset, read message | ||
| UJ cold reset | ||
| #<number> change drive numbers to <number>, swap with that device if it's already on the bus | ||
| 1571: | ||
| U0>M0 1541 mode | ||
| U0>M1 1571 mode | ||
| U0>H0 select head 0 (in 1541 mode only) | ||
| U0>H1 select head 1 (in 1541 mode only) - this is not like flipping 1541 disk, it spins the wrong way(!) | ||
| U0>V1 write verify off | ||
| U0>V0 write verify on | ||
| 1581: | ||
| /0:<name> enter partition | ||
| / change to root | ||
| SD2IEC: | ||
| CD<name> enter subfolder or disk image (D64/71/81) | ||
| CD<leftarrow> go one level up - parent folder or out of disk image | ||
| XI2 show disk images as both files (PRG) and folders (DIR) | ||
| XI1 show disk images as folder (DIR only) | ||
| XI0 disable that feature | ||
| XW save current config to EEPROM |