The host waits up to 5s after CheckRequest for TestModeChange ENTER
(8C 01 0D) before anything else, and sends no requests until the
matching EXIT (8C 00 0C) arrives; vRIO jumped straight to the
CheckReply dump, so hosts logged "RIO never came back from check
request" and skipped the version exchange. Bracket the per-board
BoardOk replies with enter/exit, byte-for-byte what the real v4.2
board sends on the wire tap.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>