Decoded from L4RIO.CPP/HPP and verified byte-for-byte against a real
v4.2 board tap: CheckRequest 80 -> board must send TestModeChange ENTER
(8C 01 0D), self-test status stream (85 <status> <unit> <ck>), EXIT
(8C 00 0C), then answer VersionRequest 81 with 86 <maj> <min> <ck>.
Full command map 80-8C both directions, ACK/retransmit rules, and the
~1ms/byte 9600-baud pacing requirement. This is the implementation spec
for the user's vRIO (virtual RIO on COM1): its missing 8C packets are
exactly why the game logs 'RIO never came back from check request!'.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
CydandClaude Fable 5
c18c253658
