make_patch.py gains --baud31250: one byte beyond the wedge patch — the SCI
init operand at $D62B ($30 -> $02). BAUD $30 = /13 prescale, /1 divider
(2MHz E / 208 = 9615); $02 = /1, /4 -> 31250 exactly, 3.3x faster. The
init write also confirms the 8MHz crystal, which is why 19200/38400 are
unreachable and why 62500/125k are left alone pending an ISR cycle count.
- 24 bytes changed vs original (sha256 9f866cf3...); re-disassembly diff
vs the classic patched image shows exactly the one operand line, and
the classic build still reproduces 3fc8170c... (script regression-safe).
- PC side: SerialPortTransport takes an optional baudRate (default 9600,
runtime untouched); RioSerialMonitor + --mash accept --baud 31250.
- Caveats documented in README/ANALYSIS: non-standard rate (FTDI-class
adapters only, no 16550s); native games still speak 9600 so this chip
is bench/RIOJoy-only; validate the wedge patch at 9600 first.
275 tests green; mash --selftest regression unchanged (FAIL/exit-1).
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
- RIOv4_2.bin: 64K image dumped from the board's AM27C512 (code at
$C000-$FFFF, TMP68HC11).
- disasm_6811.py + RIOv4_2.disasm.asm: vector-rooted 68HC11 disassembly;
SCI ISR at $D630 traced to the $2521 reply-in-progress latch leak that
wedges the analog reply path under button-mash stress.
- make_patch.py + RIOv4_2_patched.bin: two in-place edits (abort-path stub
at $DFF0, unconditional latch clear at $DA21) statically verified by
re-disassembly diff. Dynamic proof awaits a burned W27C512.
- Analysis + burn/validation plan in RIOv4_2-ANALYSIS.md and README.md.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
CydandClaude Fable 5