Atari 520ST: Difference between revisions

Line 141:

* Floppy B: not seen: check DIN‑14 drive select wiring and STF strap default (Pin 5 often wired as Drive 1 select for external B:).<ref>{{cite web |url=https://info-coach.fr/atari/hardware/interfaces.php |title=Floppy connector and BLITZ cable notes |publisher=info-coach.fr |access-date=2025-08-13}}</ref>

* ACSI devices: confirm straight‑through DB‑19M cable 1:1 to device and proper termination/ID; IRQ/REQ wiring faults present as timeouts.<ref>{{cite web |url=https://info-coach.fr/atari/hardware/interfaces.php |title=DMA/ACSI pinout and cabling |publisher=info-coach.fr |access-date=2025-08-13}}</ref>

~~== 🧠 Architecture and Processor ==~~

~~Implementation notes for engineers:~~

* The MFP’s Timer B is often used by TOS for display timing (HBLANK), Timer C drives the 200 Hz system clock; IKBD events arrive via the keyboard ACIA at 7812.5 baud (GLUE‑derived 500 kHz ÷64 for keyboard; MIDI ÷16).<ref>{{cite web |url=https://www.bighole.nl/pub/mirror/homepage.ntlworld.com/kryten_droid/Atari/ST/spg/st_prog_guide_1.htm |title=MFP timers and interrupts |publisher=Concise ST Prog Ref |access-date=2025-08-13}}</ref><ref>{{cite web |url=https://www.bighole.nl/pub/mirror/homepage.ntlworld.com/kryten_droid/Atari/ST/spg/st_prog_guide_2.htm |title=Serial/MIDI/IKBD control |publisher=Concise ST Prog Ref |access-date=2025-08-13}}</ref>

* Memory map summary for ROM and I/O: cartridge at $FA0000, TOS at $FC0000, PSG at $FF8800, DMA at $FF8600, ACIAs at $FFFC00/04, MFP at $FFFA00 region; align replacement ROMs accordingly (2‑chip vs 6‑chip variants).<ref>{{cite web |url=https://temlib.org/AtariForumWiki/index.php/Atari_ST/STe/MSTe/TT/F030_Hardware_Register_Listing |title=ST hardware register listing |publisher=AtariForumWiki |access-date=2025-08-13}}</ref><ref>{{cite web |url=https://github.com/a2ff/splitrom |title=TOS ROM splitter and motherboard notes |publisher=GitHub (splitrom) |access-date=2025-08-13}}</ref>

== Technical Documentation ==

@@ Line 141: / Line 141: @@
 * Floppy B: not seen: check DIN‑14 drive select wiring and STF strap default (Pin 5 often wired as Drive 1 select for external B:).<ref>{{cite web |url=https://info-coach.fr/atari/hardware/interfaces.php |title=Floppy connector and BLITZ cable notes |publisher=info-coach.fr |access-date=2025-08-13}}</ref>
 * ACSI devices: confirm straight‑through DB‑19M cable 1:1 to device and proper termination/ID; IRQ/REQ wiring faults present as timeouts.<ref>{{cite web |url=https://info-coach.fr/atari/hardware/interfaces.php |title=DMA/ACSI pinout and cabling |publisher=info-coach.fr |access-date=2025-08-13}}</ref>
-== 🧠 Architecture and Processor ==
-Implementation notes for engineers:
-* The MFP’s Timer B is often used by TOS for display timing (HBLANK), Timer C drives the 200 Hz system clock; IKBD events arrive via the keyboard ACIA at 7812.5 baud (GLUE‑derived 500 kHz ÷64 for keyboard; MIDI ÷16).<ref>{{cite web |url=https://www.bighole.nl/pub/mirror/homepage.ntlworld.com/kryten_droid/Atari/ST/spg/st_prog_guide_1.htm |title=MFP timers and interrupts |publisher=Concise ST Prog Ref |access-date=2025-08-13}}</ref><ref>{{cite web |url=https://www.bighole.nl/pub/mirror/homepage.ntlworld.com/kryten_droid/Atari/ST/spg/st_prog_guide_2.htm |title=Serial/MIDI/IKBD control |publisher=Concise ST Prog Ref |access-date=2025-08-13}}</ref>
-* Memory map summary for ROM and I/O: cartridge at $FA0000, TOS at $FC0000, PSG at $FF8800, DMA at $FF8600, ACIAs at $FFFC00/04, MFP at $FFFA00 region; align replacement ROMs accordingly (2‑chip vs 6‑chip variants).<ref>{{cite web |url=https://temlib.org/AtariForumWiki/index.php/Atari_ST/STe/MSTe/TT/F030_Hardware_Register_Listing |title=ST hardware register listing |publisher=AtariForumWiki |access-date=2025-08-13}}</ref><ref>{{cite web |url=https://github.com/a2ff/splitrom |title=TOS ROM splitter and motherboard notes |publisher=GitHub (splitrom) |access-date=2025-08-13}}</ref>
 == Technical Documentation ==