CydandClaude Fable 5
673cebf3b8
RIOv4_2.bin dumped from our own board EPROM (64KB, code $C000-$FFFF). Vector table confirms 68HC11: RESET->$C000, SCI serial interrupt->$D630 = the protocol state machine entry for the planned disassembly. Board patch plan steps 1-2 done (RIO-NOTES.md updated); next: disassemble from the SCI handler, find the reply-path wedge (button/event path survives it), patch, burn to a fresh EPROM, preserve the original. Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
2.0 KiB
2.0 KiB
RIO board firmware
RIOv4_2.bin— RIO cockpit I/O board firmware v4.2, dumped 2026-07-04 from one of our own boards' EPROM (64KB / 27C512-class image). sha25660a88718835c654b6135dbec7721c40ef99dca07df2ad4b57eedeb24037a5f73.
First-look analysis (from the image alone, confirmed on hardware)
- MCU: Toshiba TMP68HC11 (read off the chip; the code fingerprint
agrees — 6800-family opcodes with writes into the 68HC11 internal
register block at
$10xx). - Memory map: image is FF up to 0xC000; 16KB of code occupies
$C000-$FFFF(EPROM mapped at the top of the HC11 address space). - Startup at
$C000:SEI; LDS #$8000; STAA $1024 (TMSK2); STAA $1022 (TMSK1); ...then a longJSRinit chain — textbook HC11 bring-up. - Vector table (
$FFD6-$FFFF, big-endian):$FFFERESET →$C000$FFD6SCI (serial) →$D630— the entry point of the board's receive/protocol interrupt handler. The suspected board-side DISABLE_AND_DIE-style wedge (see RIO-NOTES.md: the board mirrors the game's PCSPAK state machine, and mash-stress leaves the reply path dead while the button/event path stays alive) is reachable from here.$FFE4→$C1B2,$FFE6→$C18E(timer output-compares); most other vectors →$DB07..$DB3Dstubs.
Why this exists
The remaining RIO reliability issue is board-side: under button-mash
stress the board's reply/analog state machine wedges (RX dead, TX alive;
a button press or power cycle revives it), reproduced identically on two
different USB serial adapters. The game-side half of the protocol was
binary-patched for tolerance (BTL4OPT patches v2-v4); the board firmware
is the other half. Plan (RIO-NOTES.md "Board firmware patch plan"):
disassemble as 68HC11 from $C000 with the vector entries as roots, find
the SCI state machine (protocol constants FC=ACK FD=NAK FE=RESTART
FF=IDLE, idle-reload-4 patterns), patch the early-ACK/error wedge path or
widen its window, burn a new EPROM, keep this original safe.