Bench refutation (display is static under axis movement; version-only
exchanges leave it alone) kills the A-9-E chord theory. Real mechanism:
the CheckRequest handler at $C5A6 runs a full self-test — sets the
test-display flag $2421, brackets itself with TestModeChange 0x8C,
lamp pattern, pod scan, five-channel encoder sweep — and returns
without repainting, leaving the channel-4 frame (04000000) as a stale
cosmetic snapshot. Board fully healthy; no reset needed. PROTOCOL.md
now warns hosts that 0x8C fires around every check. Candidate firmware
fix (repaint cave off $C5E4) noted for a future burn.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
The display observation recalibrates the counters: $3184 = give-up
cycles (once per exhausted retry sequence, not per retransmit), $3185 =
teardowns of any reply cycle needing at least one retransmission — the
counter behind a lone E0000001. Also recorded in the error-handling
inventory: 5 retransmits per cycle, reply-await arms only after the
complete frame, NAK forces exactly one counted retransmit, late ACKs
cannot rescue a cycle. (Previous commit's doc edits had silently missed
their anchors; applied properly this time.)
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Stock $D5F2 repaints the cockpit display to the E0 counter readout on
the FIRST increment of $3187/$3184/$3185, so one benign give-up shows
E0000001 forever. New opt-in make_patch.py edit 5 hijacks the render's
LDX #$2038 into a 30-byte cave at $E000: all three counters below N ->
exit via the routine's own epilogue (registers restored, display
untouched); any >= N -> resume the render. Counters still accumulate.
Built + disassembly-verified (not yet burned): RIOv4_2_patched_e0t5.bin
(9600) and RIOv4_2_patched_31250v2_e0t5.bin (FastRIO). Docs updated.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
The display has a third use: serial error annunciator. $D5F2 renders
'E0' + three live counters (TX-ring overflow $3187, reply retries
$3184, give-up teardowns $3185); $DAB8/$DAB2 is a terminal crash
screen spelling 'dEAd' when the TX dispatcher meets an unknown command
byte. Also recorded: RX overrun is unhandled (checksum NAKs are the only
symptom), unused vectors hang in BRA-self stubs, FAULT LED = MAX690 PFO,
manual/remote reset works by pulling PFI low, RUN LED = buffered AS*,
and the MAX690 watchdog is unconnected/unserviced — software wedges
persist until reset, matching bench observations.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
New display-board-1408.md: pin-level definition of the board's outputs
(8 multiplexed hex digits via ICM7228B, isolated LPT LED monitor block,
no readback path) and, from the firmware disassembly, everything the RIO
puts on it: F0 boot banner, F1 test-mode banner (keypad sequence A-9-E
enters, D exits), and the sub-test displays — five live encoder-count
readouts, button test with input index, two lamp patterns, keypad test.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
CydandClaude Fable 5