SFM is not meant to reimplement Thor. Thor is the only available teacher of the
wire protocol, but almost nothing about how it sequences its work has been shown
to be required by the device, and this document was starting to blur the two --
it said "a client should mirror it" where the honest claim is "Thor does this and
we have not checked whether the unit cares."
Adds a table separating the two, with required / not-required / unknown marked
honestly, and corrects the two places that gave Thor-copying advice.
The consequential unknowns, all testable:
* Thor's POLL -> 0x15 -> 0x49 -> POLL preamble before EVERY operation.
Plausibly required (Series III needed POLL x3 before 5A) but Thor sends it
before trivial reads too.
* 0x68 and 0x82 appear in every setup push carrying near-zero payloads that
changed nothing in either capture. If optional, our setup write is 3 frames
instead of 7 with less to get wrong. Worth settling BEFORE building the
writer.
* Whether a narrower write than the full 2,090-byte block is accepted.
One place Thor's shortcut is probably worse than the alternative: it reads with
offset=0xFFFF and skips the probe, but the probe works and reports the length
rather than making us trust a fixed one.
Two reliability problems to design against, both observed rather than assumed:
a zero ack does not mean a write applied (no failing write has ever been seen),
and nothing warns before clobbering a monitoring unit's active setup.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Ru8Lg9HkkYvX9VWWo65SmL
serversdownandClaude Opus 5
bd876b6752