ab_server answers every Execute PCCC with a fixed requestor id (pccc.c
PCCC_RESP_PREFIX: 07 3D F3 45 43 50 21) instead of echoing the request's, so
the R14-3 echo check rejected every native reply sent under the 0x1337 CIP
originator identity as BadReply. The pooled runtime now sends libplctag's
identity (PcccServices.RequestorVendor/RequestorSerial), which passes the echo
check against ab_server and against a real controller that echoes. Pinned by a
FakeEipServer round trip that answers with ab_server's fixed prefix.
ab_server's RegisterSession sanity check rejects any non-zero sender context
with encapsulation status 1 and a header-only reply, so every native session
against the simulator failed with BadCommunicationError. libplctag sends zero
(logix-register-session.hex); the codec test now matches that capture byte for
byte instead of excluding the context, and a client test pins the zero on the wire.
Scheduler tests (exclusive mid-queue and at head) and a template-reader test that
genuinely queues a Read Template behind a small read; bounded QueuedCount wait
replaces the fixed delay. Falsified: removing exclusive from the reader turns the
reader test red; removing the Exclusive handling in RequestScheduler turns all three red.
Review round 1 on the golden frames:
- Re-captured logix-read-dint-array16 (element i = ((i+1)<<24)|(i+1)) and
logix-read-bool (= 1) so neither decode oracle is all zeros. ab_server rejects
libplctag's own BOOL write with CIP 0x03 (two data bytes for a one-byte BOOL),
so the BOOL is seeded by a raw UCMM Write Tag (client seed-bool).
- Committed the capture client as scripts/ab-capture/client (outside the slnx,
CPM off, libplctag 1.5.2 pinned); capture.sh gains a `client` subcommand.
- README documents simulator-only behaviour: zeroed reply sender context, STRING
typed D0 00 instead of A0 02 + handle, and the BOOL write refusal.
- capture.sh no longer claims UnregisterSession reaches the wire (session ends in RST).
- CaptureFileTests also check the CPF walk ends at the frame end and that every
reply service is its request service | 0x80.
17 .hex fixtures captured from libplctag 1.5.2 (native 2.6.0) against
otopcua-ab-server:libplctag-release, plus the CaptureFile loader, its
length/alternation tests, and the re-runnable scripts/ab-capture/capture.sh.
Observed and recorded in Captures/README.md "Routing observed":
- Micro800 is NOT UCMM under libplctag 2.6.0: it opens a Large Forward Open
(path 20 02 24 01) and reads connected; use_connected_msg=0 is ignored.
- SLC500/MicroLogix/PLC-5 send Execute PCCC 0x4B unconnected and unwrapped;
a configured path=1,0 never reaches the wire.
- Only Large FO 0x5B was observed; no 0x54 fallback occurred.
- LogixPccc is unreachable against ab_server (CIP 0x08); no fixture committed.
Found by the read-only live gate against the TwinCAT 2.11 Elma cleaners
Z33856 / Z33733:
- The Beckhoff library reports a TC2 dotted MEMBER symbol's ByteSize as if the
PLC's byte count were a bit count (STRING(80) -> 11, INT -> 1, UDINT -> 1)
while DataType.ByteSize is right (81/2/4, raw SYM_INFOBYNAMEEX says 81). The
previous commit's typeof(byte[]) read sliced by the symbol size, so
.OPC_MACHINEDATA.PROCESSSTATUS read "ready for o" at Good; the notification
width check would also have refused every numeric member. The shape now takes
the resolved type's size, and string reads go by index group/offset (or a
fresh handle for 0xF005) at that width.
- P_INITINPUT_ACTION.SLOTID is "STRING(20) (VAR_IN_OUT)" - a 4-byte reference -
but resolves to a plain STRING(20); a String tag read 21 bytes at the pointer
as text at Good. The symbol's own VAR_IN_OUT marker now classifies it
NonScalar -> BadTypeMismatch.
libplctag decodes whatever bytes the controller returns as the authored type and never
checks the CIP type code. Live read-only check on a production press: WW_ActualVacuum is a
REAL (L5X + the controller's symbol table agree) but the legacy Kepware export in the
ignitionoee repo types it Short; read as INT it returned Good -17346 while the real value
was 5.37. A scalar atomic read (not an array, not a bit-in-DINT) whose buffer size is not
the authored type's width now reads BadTypeMismatch with a warning naming both. Widths
observed live: SINT/BOOL 1, INT 2, DINT/REAL 4, LINT 8. IAbCipTagRuntime.GetSize() is a
default-interface member (-1 = unknown, never checked). Same-width mismatches (DINT vs
REAL) stay undetectable without the type code libplctag strips.
The mock had served the shapes the driver once agreed with it on, so it
validated the very defects just fixed: it ANSWERED the non-existent 0x00D3
cnc_getfigure, wrote base/exponent 0/0 into position blocks, put the macro
decimal at offset 4, and served spindle 'max rpm' as a raw constant.
Ported from the sister ignitionoee mock (local divergence recorded in
VENDORED.md; the LE timer and alarm cap are kept):
- 0x00D3 refused with EW_FUNC, as the real control does.
- 0x0026 blocks carry base 10 / position_figures exponent; signed arg2,
arg2 = 0 or past the axis count refused EW_ATTRIB.
- cnc_rdmacro is the 8-byte ODBM shape, 9-digit mantissa, unset = vacant.
- servo/spindle meter records carry the envelope; spindle meters are
1/16384-of-full-scale counts (motor speed = speed / max_rpm).
Integration tests: spindle test reads Load/MotorSpeedPct percentages; the
position-scale test now proves the block's own scale wins; new
Vacant_positions_and_macros_read_bad_over_the_wire. 12/12 pass against the
mock run locally (python -m focas_mock.cli serve, OTOPCUA_FOCAS_SIM_ENDPOINT).
Live read-only check against a production CompactLogix press: Program:UN01_Press._ModeNames
(STR0016[32], 4 elements requested) returned an 80-byte buffer with libplctag.NET 1.5.2's
ElementSize unset. The driver fell back to the static 88-byte STRING stride, read element
1 past the buffer, and the whole read failed (ErrorOutOfBounds -> BadCommunicationError).
When the buffer divides evenly by the element count, that quotient is now the stride;
the read returns [undefined, Production, Maintenance, Manual] as the controller holds.
Live read-only check against a production CompactLogix press: with one nonexistent tag
first in the read list, libplctag's create threw LibPlcTagException("ErrorNotFound"); the
driver counted it as a failed Forward-Open, opened the device's 05/STAB-8 connect-backoff
window, and every other cold tag on the device - all real (WW_InCycle, WW_ActualPress,
WW_WorkOrderNum) - read BadCommunicationError. In steady polling the bad tag re-opens
the window each attempt, so siblings ordered after it may never connect.
- A create that fails with a "controller answered" status (NotFound/NoMatch/BadDevice,
the probe's existing reachable classification) records backoff SUCCESS, not failure.
Genuine connection failures still open the window (falsification control test).
- Read exceptions map through the libplctag Status they carry: unknown tag ->
BadNodeIdUnknown, decode past the buffer -> BadOutOfRange, timeout -> BadTimeout,
instead of a blanket BadCommunicationError. One status-name parser
(AbCipStatusMapper.TryGetStatus) now serves both the read path and the probe.
WireFocasClient.GetProgramInfoAsync defaulted every field the CNC did not report:
ONumber ?? 0 when the cnc_exeprgname2 payload was too short to carry it, and
Name '' / BlockCount 0 / Mode 0 when the sub-read was refused. 0 is a genuine
O-number (a 31i reports 0 for a path-executed program -- live Z-34184), a
genuine block count, and Mode 0 is MDI, a real operating mode.
FocasProgramInfo fields are now nullable; MapProgramInfo leaves unreported
fields null and the fixed tree publishes them BadNoData while the bundle's
other fields stay Good.
Ported from the sister ignitionoee FOCAS driver (101a3b1, 2026-08-12).
Live read-only check: a production CompactLogix lists the module tag ABB_OmniCore:I in
@tags and libplctag reads ABB_OmniCore:I.ConnectionFaulted without complaint, but the
driver refused the path as malformed (identifier rule had no colon) and reported the
tag BadCommunicationError. Colon-separated identifier/slot parts are now legal in the
controller-scope base segment only (never past it, never under Program: scope).
Servo (0x0056) and spindle (0x0040) meter records are 8 bytes:
[i32 value][u16 base][u16 exponent], the same self-describing envelope as the
position blocks.
Servo: offset 4 was read as a decimal count. It is the BASE (a steady 10), so
every load was divided by 10^10 and published ~0 -- the sister ignitionoee panel
read servo 0% on every axis of a Makino cutting at 20,000 rpm. Loads are now
value / base^exponent, a direct percentage.
Spindle: the raw meter is a 1/16384 fraction of full scale. Settled on the real
Z-34184 by regressing the type-1 meter against cnc_rddynamic2 spindle speed over
596..20,000 rpm (rpm = 1.220749 x meter; 16384 x 1.220749 = 20000.75). So:
- Spindle/{name}/Load publishes % of rated load (Float64; was the raw Int32
count -- a reading of 9155 meant 55.9%).
- Spindle/{name}/MaxRpm is RENAMED Spindle/{name}/MotorSpeedPct (Float64, % of
maximum speed) and is polled with Load. The old node was actively wrong: the
type-1 meter is the live motor speed, and it was read once at bootstrap and
served forever as if it were a max-RPM constant. Client-visible: FIXED: tags
on .../MaxRpm must be re-pointed.
- The spindle read no longer stops at the first zero after slot 1 (which dropped
an idle second spindle and kept non-zero residue); every slot is returned.
A record whose envelope is undescribable (base not 2/10, exponent > 18 -- e.g.
residue past the configured axis/spindle count) publishes BadNoData, never a Good 0.
Ported from the sister ignitionoee FOCAS driver v0.17.2/v0.17.3 (Focas.Wire-019);
live captures live-spmeter-{load,maxrpm}-0x0040.bin added as fixtures.
Joseph Doherty