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docs(ab): hw4 evidence fix round 1 - bit-write gap provenance, README/CLI/fixture docs, libplctag-deletion gap

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Claude-Session: https://claude.ai/code/session_01Ef2ozxS7QPanGT8uoATbTe
This commit is contained in:
Joseph Doherty
2026-10-09 04:12:53 -04:00
parent 14ec145487
commit 9e894decb0
7 changed files with 37 additions and 31 deletions
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docs/drivers/AbCip.md
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@@ -243,7 +243,8 @@ The driver has two interchangeable wire transports, selected by one `DriverConfi
Good). Still ab_server-only: array, STRING and UDT-member writes and fragmented writes. Mixed STRING/array/scalar
Multiple Service Packet reads (#582) are proven on the press (one 5-read MSP, values equal to single reads). Results:
[native-ab-transport-gate-results](../plans/2026-10-07-native-ab-transport-gate-results.md).
- **libplctag cannot be deleted** until a bench controller allows write verification.
- **libplctag cannot be deleted yet.** Scalar native writes are proven on a CompactLogix (2026-10-09); what remains is #567
(fragmented wide-struct writes), array/STRING/UDT-member writes on hardware, and AbLegacy native (simulator-only, no PCCC hardware).
- ⚠️ RESIDUAL (#567): wide-struct **fragmented writes** (8-byte alignment) are unit-tested only. Production
presses are read-only and there is no bench controller, so this cannot be proven; it stays open until a
bench controller exists.
docs/drivers/AbLegacy-Test-Fixture.md
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@@ -11,8 +11,8 @@ for N-file (Int16), F-file (Float32), and L-file (Int32) reads across all
three families when `AB_LEGACY_CIP_PATH=1,0` (the default). The earlier
`BadCommunicationError` was traced to `ab_server` requiring a non-empty CIP
routing path before forwarding to the PCCC dispatcher — the `/1,0` workaround
resolves it (see `Docker/README.md §Known limitations`). Residual gap: bit-file
writes (`B3:0/5`) still surface `0x803D0000` against `ab_server`. Unit tests
resolves it (see `Docker/README.md §Known limitations`). The old bit-file write
gap (`B3:0/5` giving `0x803D0000`) no longer reproduces (2026-10-09, `AbLegacyBitWriteTests`). Unit tests
via `FakeAbLegacyTag` carry full contract coverage for all paths.
## What the fixture is
@@ -105,12 +105,10 @@ cover the common ones but uncommon ones (`R` counters, `S` status files,
## Follow-up candidates
1. **Close residual ab_server bit-file write gap** — N (Int16), F (Float32),
and L (Int32) files round-trip cleanly across SLC500 / MicroLogix / PLC-5
modes with the `/1,0` cip-path workaround in place. Remaining gap: bit-file
writes (`B3:0/5`) surface `0x803D0000` against `ab_server --plc=SLC500`.
Contributing a patch to `libplctag/libplctag` to close this would remove
the last Docker-vs-hardware divergence for bit writes.
1. **(Closed, 2026-10-09) ab_server bit-file write gap** — N, F and L files
round-trip with the `/1,0` workaround, and `B3:0/5` bit writes now pass on
SLC500/MicroLogix (both transports; `AbLegacyBitWriteTests`). The May 2026
`0x803D0000` does not reproduce; its cause is undetermined.
2. **Rockwell RSEmulate 500 golden-box tier** — Rockwell's real emulator
for SLC/MicroLogix/PLC-5. Would close UDT-equivalent (integer-file
indirection), timer/counter decomposition, and real ladder execution
docs/drivers/AbLegacy.md
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@@ -219,7 +219,7 @@ Everything below is against the `ab_server` simulator; no real PCCC controller h
| F-file read (`F8`) | one capture, `slc500-read-f8` (codec parity only; no native F write on a wire) |
| S (incl. the default probe `S:0`), B, T, C, R, L, ST, A, O, I | **none** — encoded from the PCCC file-type table |
| MicroLogix function files (RTC/HSC/...), PLC-5 octal I/O | **none** — parsed only; native refuses function files as Unsupported |
| Bit-within-word write (`B3:0/5`) | `ab_server` SLC500 + MicroLogix, both transports (`AbLegacyBitWriteTests`): the driver RMWs the parent word, only the addressed bit changes. PLC-5 native refuses it (`BadNotSupported`, #571) |
| Bit-within-word write (`B3:0/5`) | `ab_server` SLC500 + MicroLogix, both transports (`AbLegacyBitWriteTests`): the driver RMWs the parent word, only the addressed bit changes (the parent-word read-modify-write is not atomic against ladder writes to the same word). PLC-5 native refuses it (`BadNotSupported`, #571) |
| Indirect addressing (`N7:[N7:0]`) | `ab_server` N-file, both transports (#646) - resolved by the driver, the transport sees the composed address |
| T/C/R sub-elements (`.PRE`/`.ACC`/`.LEN`/`.POS`), 6-byte T/C/R element layout | **none** |