Merge b640-focas: FOCAS Status/ subtree, PMC range coalescing, parts-count docs (#257 #266 #258, tracker #633)

Claude-Session: https://claude.ai/code/session_01Ef2ozxS7QPanGT8uoATbTe

src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.FOCAS.Contracts/FocasDriverOptions.cs

@@ -31,6 +31,8 @@ public sealed class FocasDriverOptions
     public FocasHandleRecycleOptions HandleRecycle { get; init; } = new();
     /// <summary>Gets the fixed tree options.</summary>
     public FocasFixedTreeOptions FixedTree { get; init; } = new();
+    /// <summary>Gets the PMC range-coalescing options (Gitea #266).</summary>
+    public FocasPmcCoalesceOptions PmcCoalesce { get; init; } = new();
 
     /// <summary>
     ///     Timeout for the AdminUI Test Connect probe, in seconds. The AdminUI clamps to a
@@ -41,6 +43,32 @@ public sealed class FocasDriverOptions
     public int ProbeTimeoutSeconds { get; init; } = 10;
 }
 
+/// <summary>
+///     Merges adjacent / near PMC reads in one poll batch into fewer <c>pmc_rdpmcrng</c> calls (Gitea #266).
+///     On by default: a batch with a single PMC tag per area is unaffected, and a coalesced read the CNC
+///     rejects falls back to per-tag reads, so enabling it cannot make a readable tag unreadable.
+/// </summary>
+public sealed class FocasPmcCoalesceOptions
+{
+    /// <summary>Gets a value indicating whether PMC coalescing is on.</summary>
+    public bool Enabled { get; init; } = true;
+
+    /// <summary>
+    ///     Largest range, in bytes, one coalesced read may cover. Bounds the response size and the
+    ///     blast radius of a rejected range. Default 128.
+    /// </summary>
+    [Range(1, 1024)]
+    public int MaxSpanBytes { get; init; } = 128;
+
+    /// <summary>
+    ///     Largest run of bytes nobody asked for that may sit between two merged tags. Reading a few
+    ///     spare bytes is cheaper than a second round-trip, but every spare byte must be a valid PMC
+    ///     address on the CNC. Default 8; 0 merges only strictly adjacent tags.
+    /// </summary>
+    [Range(0, 1024)]
+    public int MaxGapBytes { get; init; } = 8;
+}
+
 /// <summary>
 ///     Fixed-node tree exposed by FOCAS per <c>docs/v2/driver-specs.md §7</c> —
 ///     <c>Identity/</c>, <c>Axes/{name}/</c>, etc. populated from

src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.FOCAS/FocasDriver.cs

@@ -498,8 +498,16 @@ public sealed class FocasDriver : IDriver, IReadable, IWritable, ITagDiscovery,
         var now = DateTime.UtcNow;
         var results = new DataValueSnapshot[fullReferences.Count];
 
+        // #266 — merge adjacent / near PMC reads of one device into fewer pmc_rdpmcrng calls. Indices it
+        // serves are marked here and skipped by the per-tag loop below; everything else (including every
+        // single-tag range and any range the CNC rejected) takes the unchanged per-tag path.
+        var served = _options.PmcCoalesce.Enabled
+            ? await CoalescePmcReadsAsync(fullReferences, results, now, cancellationToken).ConfigureAwait(false)
+            : null;
+
         for (var i = 0; i < fullReferences.Count; i++)
         {
+            if (served is not null && served[i]) continue;
             var reference = fullReferences[i];
 
             // Fixed-tree T1 — fixed-tree references are synthesized from the cached
@@ -581,6 +589,127 @@ public sealed class FocasDriver : IDriver, IReadable, IWritable, ITagDiscovery,
         return results;
     }
 
+    /// <summary>
+    ///     PMC coalescing pre-pass (Gitea #266). Groups the batch's PMC tags by device, plans merged ranges
+    ///     (<see cref="FocasPmcCoalescer"/>) and serves every multi-member range with ONE
+    ///     <c>pmc_rdpmcrng</c>, slicing each tag's value out of the returned slots.
+    /// </summary>
+    /// <remarks>
+    ///     Failure handling is the point of the design. A rejected range is NOT mis-attributed to its members:
+    ///     <list type="bullet">
+    ///       <item>a comms-level failure (timeout / transport) fails every member with that status — the
+    ///       link is down, so re-reading each member would multiply timeouts;</item>
+    ///       <item>any other non-Good status (typically a spare "gap" byte that is not a valid PMC address)
+    ///       leaves the members UNSERVED, so the per-tag loop reads them individually and each gets its own
+    ///       true status — and the range is remembered so later polls skip the doomed merged read.</item>
+    ///     </list>
+    ///     Returns null when nothing was served.
+    /// </remarks>
+    private async Task<bool[]?> CoalescePmcReadsAsync(
+        IReadOnlyList<string> references, DataValueSnapshot[] results, DateTime now, CancellationToken ct)
+    {
+        Dictionary<DeviceState, List<FocasPmcReadItem>>? byDevice = null;
+        for (var i = 0; i < references.Count; i++)
+        {
+            try
+            {
+                var reference = references[i];
+                if (_fixedTreeActive && TryReadFixedTree(reference, now) is not null) continue;
+                if (!_resolver.TryResolve(reference, out var def)) continue;
+                if (!_devices.TryGetValue(def.DeviceHostAddress, out var device)) continue;
+                var parsed = ResolveParsedAddress(def);
+                if (parsed.Kind != FocasAreaKind.Pmc || parsed.PmcLetter is null) continue;
+                (byDevice ??= []).TryAdd(device, []);
+                byDevice[device].Add(new FocasPmcReadItem(i, parsed.PmcLetter, parsed.Number, def.DataType, parsed.BitIndex));
+            }
+            catch (Exception ex) when (ex is not OperationCanceledException)
+            {
+                /* malformed / unresolvable — the per-tag loop reports it with its usual status */
+            }
+        }
+        if (byDevice is null) return null;
+
+        bool[]? served = null;
+        foreach (var (device, items) in byDevice)
+        {
+            if (items.Count < 2) continue;
+            var plans = FocasPmcCoalescer.Plan(items, _options.PmcCoalesce.MaxSpanBytes, _options.PmcCoalesce.MaxGapBytes);
+            if (!plans.Any(p => p.Members.Count >= 2 && !device.CoalesceRejected.ContainsKey(p.Key))) continue;
+
+            // One connect attempt per device per batch: if it fails, every PMC tag of the device fails with
+            // that status here instead of paying a connect attempt per plan and again per tag.
+            IFocasClient client;
+            try { client = await EnsureConnectedAsync(device, ct).ConfigureAwait(false); }
+            catch (OperationCanceledException) when (ct.IsCancellationRequested) { throw; }
+            catch (Exception)
+            {
+                FailMembers(items, FocasStatusMapper.BadCommunicationError, references, results, now, ref served,
+                    $"FOCAS connect failed reading PMC tags of {device.Options.HostAddress}");
+                continue;
+            }
+
+            foreach (var plan in plans)
+            {
+                if (plan.Members.Count < 2) continue;
+                if (device.CoalesceRejected.ContainsKey(plan.Key)) continue;
+
+                var members = plan.Members;
+                try
+                {
+                    var (slots, status) = await client
+                        .ReadPmcSlotsAsync(plan.Letter, plan.SlotType, plan.Start, plan.End, ct)
+                        .ConfigureAwait(false);
+
+                    if (status == FocasStatusMapper.Good && slots is not null)
+                    {
+                        foreach (var m in members)
+                        {
+                            var slot = plan.SlotOf(m);
+                            results[m.Index] = slot < slots.Count
+                                ? new DataValueSnapshot(FocasPmcCoalescer.MapSlot(slots[slot], m.Type, m.BitIndex), status, now, now)
+                                : new DataValueSnapshot(null, FocasStatusMapper.BadOutOfRange, now, now);
+                            (served ??= new bool[references.Count])[m.Index] = true;
+                        }
+                        Volatile.Write(ref _health, new DriverHealth(DriverState.Healthy, now, null));
+                    }
+                    else
+                    {
+                        // The CNC REFUSED the merged range (any return code, mapped or not). Don't guess which
+                        // member is at fault: let the per-tag loop give each its own answer. Remember the range
+                        // so later polls skip the doomed read — except for a transient refusal (EW_BUSY maps to
+                        // BadDeviceFailure), which says nothing about the range.
+                        if (status != FocasStatusMapper.BadDeviceFailure)
+                            device.CoalesceRejected[plan.Key] = 0;
+                        _logger.LogDebug(
+                            "FOCAS PMC range {Key} on {Host} rejected (0x{Status:X8}) — reading its {Count} tags individually",
+                            plan.Key, device.Options.HostAddress, status, members.Count);
+                    }
+                }
+                catch (OperationCanceledException) when (ct.IsCancellationRequested) { throw; }
+                catch (Exception)
+                {
+                    // Transport failure / timeout: the link is suspect, so fail the members without per-tag retries.
+                    FailMembers(members, FocasStatusMapper.BadCommunicationError, references, results, now, ref served,
+                        $"FOCAS transport failure reading PMC range {plan.Key}");
+                }
+            }
+        }
+        return served;
+
+        void FailMembers(IEnumerable<FocasPmcReadItem> failed, uint status, IReadOnlyList<string> refs,
+            DataValueSnapshot[] res, DateTime stamp, ref bool[]? servedRef, string reason)
+        {
+            foreach (var m in failed)
+            {
+                res[m.Index] = new DataValueSnapshot(null, status, null, stamp);
+                (servedRef ??= new bool[refs.Count])[m.Index] = true;
+            }
+            Volatile.Write(ref _health, new DriverHealth(DriverState.Degraded,
+                Volatile.Read(ref _health).LastSuccessfulRead,
+                $"{reason} (0x{status:X8})"));
+        }
+    }
+
     // ---- IWritable ----
 
     /// <inheritdoc />
@@ -751,6 +880,15 @@ public sealed class FocasDriver : IDriver, IReadable, IWritable, ITagDiscovery,
                     EmitFixedVariable(opMode, "OperationMode", "ModeText", DriverDataType.String);
                 }
 
+                // Fixed-tree T2.5 — Status subtree (cnc_statinfo flags, #257), gated on its own probe.
+                if (cache.Capabilities.Status)
+                {
+                    var status = deviceFolder.Folder("Status", "Status");
+                    foreach (var field in StatusFields)
+                        EmitFixedVariable(status, "Status", field, DriverDataType.Int32);
+                    EmitFixedVariable(status, "Status", "RunText", DriverDataType.String);
+                }
+
                 // Fixed-tree T3 — Timers subtree (power-on / operating / cutting / cycle).
                 if (cache.Capabilities.Timers)
                 {
@@ -1008,6 +1146,7 @@ public sealed class FocasDriver : IDriver, IReadable, IWritable, ITagDiscovery,
                 var servoLoads = await SafeProbe(() => client.GetServoLoadsAsync(ct), []);
                 var programInfo = await SafeTryProbe(() => client.GetProgramInfoAsync(ct));
                 var timer = await SafeTryProbe(() => client.GetTimerAsync(FocasTimerKind.PowerOn, ct));
+                var statusProbe = await SafeTryProbe(() => client.GetStatusAsync(ct));
                 var spindleLoad = await SafeProbe(() => client.GetSpindleLoadsAsync(ct), []);
 
                 var caps = new FocasFixedTreeCapabilities(
@@ -1016,7 +1155,9 @@ public sealed class FocasDriver : IDriver, IReadable, IWritable, ITagDiscovery,
                     SpindleMotorSpeed: spindleMotorSpeeds.Count > 0,
                     ServoLoad: servoLoads.Count > 0,
                     ProgramInfo: programInfo is not null,
-                    Timers: timer is not null);
+                    Timers: timer is not null,
+                    Status: statusProbe is not null);
+                state.LastStatus = statusProbe;
 
                 state.FixedTreeCache = new FocasFixedTreeCache(sys, [.. axes], [.. spindles], caps);
                 // The bootstrap IS an answer from the device, and Identity comes entirely from it —
@@ -1054,6 +1195,7 @@ public sealed class FocasDriver : IDriver, IReadable, IWritable, ITagDiscovery,
 
         var programPollDue = DateTime.MinValue;
         var timerPollDue = DateTime.MinValue;
+        var statusPollDue = DateTime.MinValue;
         while (!ct.IsCancellationRequested)
         {
             try
@@ -1129,6 +1271,20 @@ public sealed class FocasDriver : IDriver, IReadable, IWritable, ITagDiscovery,
                     programPollDue = DateTime.UtcNow + programInterval;
                 }
 
+                // Status flags (cnc_statinfo, #257) — same cadence as program/mode: run/emergency/alarm
+                // transitions are operator-timescale events and one call returns all of them.
+                if (cache.Capabilities.Status
+                    && programInterval > TimeSpan.Zero && DateTime.UtcNow >= statusPollDue)
+                {
+                    try { state.LastStatus = await client.GetStatusAsync(ct).ConfigureAwait(false); }
+                    catch (Exception ex)
+                    {
+                        /* transient — keep the last value; staleness is dated by LastFixedPollUtc */
+                        _logger.LogDebug(ex, "FOCAS status poll failed for {Host}", state.Options.HostAddress);
+                    }
+                    statusPollDue = DateTime.UtcNow + programInterval;
+                }
+
                 // Timers — slowest cadence. Fires 4 FWLIB calls per tick (one per kind).
                 var timerInterval = _options.FixedTree.TimerPollInterval;
                 if (cache.Capabilities.Timers
@@ -1245,6 +1401,8 @@ public sealed class FocasDriver : IDriver, IReadable, IWritable, ITagDiscovery,
         }
     }
 
+    private static readonly string[] StatusFields = ["Auto", "Run", "Motion", "Mstb", "Emergency", "Alarm", "Edit", "TmMode"];
+
     private static object? TimerValue(DeviceState state, FocasTimerKind kind) =>
         state.LastTimers.TryGetValue(kind, out var t) ? (object)t.TotalSeconds : null;
 
@@ -1385,6 +1543,15 @@ public sealed class FocasDriver : IDriver, IReadable, IWritable, ITagDiscovery,
                 "OperationMode/Mode" => state.LastProgramInfo?.Mode,
                 "OperationMode/ModeText" => state.LastProgramInfo?.Mode is { } mode
                     ? FocasOpMode.ToText(mode) : null,
+                "Status/Auto" => state.LastStatus?.Auto,
+                "Status/Run" => state.LastStatus?.Run,
+                "Status/Motion" => state.LastStatus?.Motion,
+                "Status/Mstb" => state.LastStatus?.Mstb,
+                "Status/Emergency" => state.LastStatus?.Emergency,
+                "Status/Alarm" => state.LastStatus?.Alarm,
+                "Status/Edit" => state.LastStatus?.Edit,
+                "Status/TmMode" => state.LastStatus?.TmMode,
+                "Status/RunText" => state.LastStatus is { } st ? FocasRunState.ToText(st.Run) : null,
                 "Timers/PowerOnSeconds" => TimerValue(state, FocasTimerKind.PowerOn),
                 "Timers/OperatingSeconds" => TimerValue(state, FocasTimerKind.Operating),
                 "Timers/CuttingSeconds" => TimerValue(state, FocasTimerKind.Cutting),
@@ -1618,7 +1785,8 @@ public sealed class FocasDriver : IDriver, IReadable, IWritable, ITagDiscovery,
         bool SpindleMotorSpeed, // cnc_rdspmeter type 1 (motor speed) bootstrap probe succeeded
         bool ServoLoad,         // cnc_rdsvmeter bootstrap probe returned data
         bool ProgramInfo,       // cnc_exeprgname2 + cnc_rdblkcount + cnc_rdopmode work
-        bool Timers);           // cnc_rdtimer works for at least PowerOn
+        bool Timers,            // cnc_rdtimer works for at least PowerOn
+        bool Status = false);   // cnc_statinfo answered at bootstrap (#257)
 
     internal sealed class DeviceState(FocasHostAddress parsedAddress, FocasDeviceOptions options)
     {
@@ -1683,6 +1851,13 @@ public sealed class FocasDriver : IDriver, IReadable, IWritable, ITagDiscovery,
         ///     holding no value.
         /// </summary>
         public ConcurrentDictionary<string, double> LastFixedSnapshots { get; } = new(StringComparer.OrdinalIgnoreCase);
+        /// <summary>
+        ///     PMC ranges (<see cref="FocasPmcRangePlan.Key"/>) the CNC rejected as a merged read, so later polls skip
+        ///     straight to per-tag reads instead of paying a doomed round-trip every cycle (#266).
+        /// </summary>
+        public ConcurrentDictionary<string, byte> CoalesceRejected { get; } = new(StringComparer.Ordinal);
+        /// <summary>Gets or sets the last <c>cnc_statinfo</c> snapshot (#257); null until the first answer.</summary>
+        public FocasStatus? LastStatus { get; set; }
         /// <summary>Gets or sets the last program information snapshot.</summary>
         public FocasProgramInfo? LastProgramInfo { get; set; }
         /// <summary>Gets or sets the cached first-axis dynamic snapshot — feeds Program/Number, /MainNumber, /Sequence.</summary>

src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.FOCAS/FocasDriverFactoryExtensions.cs

@@ -115,6 +115,7 @@ public static class FocasDriverFactoryExtensions
             FixedTree = BuildFixedTree(dto.FixedTree),
             AlarmProjection = BuildAlarmProjection(dto.AlarmProjection),
             HandleRecycle = BuildHandleRecycle(dto.HandleRecycle),
+            PmcCoalesce = BuildPmcCoalesce(dto.PmcCoalesce),
         };
 
         return new FocasDriverBinding(options, BuildClientFactory(dto, driverInstanceId, loggerFactory));
@@ -206,6 +207,19 @@ public static class FocasDriverFactoryExtensions
         };
     }
 
+    /// <summary>Map the optional <c>PmcCoalesce</c> section; a missing section or key keeps the default.</summary>
+    private static FocasPmcCoalesceOptions BuildPmcCoalesce(FocasPmcCoalesceDto? dto)
+    {
+        var defaults = new FocasPmcCoalesceOptions();
+        if (dto is null) return defaults;
+        return new FocasPmcCoalesceOptions
+        {
+            Enabled = dto.Enabled ?? defaults.Enabled,
+            MaxSpanBytes = dto.MaxSpanBytes is > 0 ? dto.MaxSpanBytes.Value : defaults.MaxSpanBytes,
+            MaxGapBytes = dto.MaxGapBytes is >= 0 ? dto.MaxGapBytes.Value : defaults.MaxGapBytes,
+        };
+    }
+
     private static FocasCncSeries ParseSeries(string? raw)
     {
         if (string.IsNullOrWhiteSpace(raw)) return FocasCncSeries.Unknown;
@@ -284,6 +298,9 @@ public static class FocasDriverFactoryExtensions
 
         /// <summary>Gets or sets the handle recycle configuration options.</summary>
         public FocasHandleRecycleDto? HandleRecycle { get; init; }
+
+        /// <summary>Gets or sets the PMC range-coalescing configuration options.</summary>
+        public FocasPmcCoalesceDto? PmcCoalesce { get; init; }
     }
 
     internal sealed class FocasDeviceDto
@@ -348,6 +365,17 @@ public static class FocasDriverFactoryExtensions
         public TimeSpan? PollInterval { get; init; }
     }
 
+    /// <summary>Optional <c>PmcCoalesce</c> config section (#266).</summary>
+    internal sealed class FocasPmcCoalesceDto
+    {
+        /// <summary>Gets or sets a value indicating whether coalescing is on.</summary>
+        public bool? Enabled { get; init; }
+        /// <summary>Gets or sets the largest coalesced range in bytes.</summary>
+        public int? MaxSpanBytes { get; init; }
+        /// <summary>Gets or sets the largest tolerated gap in bytes.</summary>
+        public int? MaxGapBytes { get; init; }
+    }
+
     /// <summary>Optional <c>HandleRecycle</c> config section.</summary>
     internal sealed class FocasHandleRecycleDto
     {

src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.FOCAS/FocasPmcCoalescer.cs

@@ -0,0 +1,137 @@
+using ZB.MOM.WW.OtOpcUa.Driver.FOCAS.Wire;
+
+namespace ZB.MOM.WW.OtOpcUa.Driver.FOCAS;
+
+/// <summary>One PMC read the coalescer may merge — the caller's batch index plus the parsed address and type.</summary>
+/// <param name="Index">Position in the caller's batch; results are sliced back to it.</param>
+/// <param name="Letter">PMC area letter (<c>R</c>, <c>X</c>, ...), upper-case.</param>
+/// <param name="Number">Byte address.</param>
+/// <param name="Type">The tag's declared data type (decides slot width and decode).</param>
+/// <param name="BitIndex">Bit index for a <see cref="FocasDataType.Bit"/> tag.</param>
+internal readonly record struct FocasPmcReadItem(int Index, string Letter, int Number, FocasDataType Type, int? BitIndex);
+
+/// <summary>
+///     One planned <c>pmc_rdpmcrng</c> read covering <see cref="Members"/>. <see cref="End"/> is inclusive and is a
+///     whole number of <see cref="SlotWidth"/>-byte slots from <see cref="Start"/>.
+/// </summary>
+internal sealed record FocasPmcRangePlan(
+    string Letter,
+    FocasDataType SlotType,
+    int SlotWidth,
+    int Start,
+    int End,
+    IReadOnlyList<FocasPmcReadItem> Members)
+{
+    /// <summary>Stable key for the "this range was rejected, read members individually" memo.</summary>
+    public string Key => $"{Letter}:{SlotType}:{Start}-{End}";
+
+    /// <summary>Slot index (into the decoded range) that holds <paramref name="item"/>'s value.</summary>
+    /// <param name="item">A member of this plan.</param>
+    /// <returns>The zero-based slot index.</returns>
+    public int SlotOf(FocasPmcReadItem item) => (item.Number - Start) / SlotWidth;
+}
+
+/// <summary>
+///     Merges adjacent / near PMC reads in one poll batch into fewer <c>pmc_rdpmcrng</c> calls (Gitea #266).
+/// </summary>
+/// <remarks>
+///     <para>Items are grouped by <c>(letter, slot width class)</c> and merged in address order while (a) the gap to
+///     the previous member is at most <c>maxGapBytes</c> and (b) the whole range stays within <c>maxSpanBytes</c>.
+///     A multi-byte member only joins a range when its offset from the range start is a multiple of its width — the
+///     CNC splits a range into width-sized slots from the start, so an unaligned member would be decoded from the
+///     wrong bytes. Members that cannot merge become single-member plans; the driver reads those through the
+///     ordinary per-tag path, so the common "one tag per area" case is byte-for-byte unchanged.</para>
+///     <para>Pure and deterministic: no I/O, no clock.</para>
+/// </remarks>
+internal static class FocasPmcCoalescer
+{
+    /// <summary>Plans the reads for a batch.</summary>
+    /// <param name="items">The PMC reads in the batch (any order).</param>
+    /// <param name="maxSpanBytes">Largest range, in bytes, one coalesced read may cover (&gt;= 1).</param>
+    /// <param name="maxGapBytes">Largest run of unrequested bytes tolerated between two members (&gt;= 0).</param>
+    /// <returns>Range plans; every input item appears in exactly one plan.</returns>
+    public static IReadOnlyList<FocasPmcRangePlan> Plan(
+        IEnumerable<FocasPmcReadItem> items, int maxSpanBytes, int maxGapBytes)
+    {
+        maxSpanBytes = Math.Max(1, maxSpanBytes);
+        maxGapBytes = Math.Max(0, maxGapBytes);
+        var plans = new List<FocasPmcRangePlan>();
+
+        var groups = items
+            .GroupBy(i => (Letter: i.Letter.ToUpperInvariant(), Slot: SlotTypeOf(i.Type)))
+            .OrderBy(g => g.Key.Letter, StringComparer.Ordinal).ThenBy(g => g.Key.Slot);
+
+        foreach (var group in groups)
+        {
+            var width = FocasWireClient.PmcByteWidth((short)FocasPmcDataTypeLookup.FromFocasDataType(group.Key.Slot));
+            var sorted = group.OrderBy(i => i.Number).ThenBy(i => i.Index).ToList();
+
+            List<FocasPmcReadItem>? members = null;
+            var start = 0;
+            var end = 0; // inclusive
+
+            void Flush()
+            {
+                if (members is null) return;
+                // Round the range up to a whole number of slots so the CNC returns no partial trailing slot.
+                var bytes = end - start + 1;
+                var rounded = (bytes + width - 1) / width * width;
+                plans.Add(new FocasPmcRangePlan(group.Key.Letter, group.Key.Slot, width, start, start + rounded - 1, members));
+                members = null;
+            }
+
+            foreach (var item in sorted)
+            {
+                var itemEnd = item.Number + width - 1;
+                if (members is not null)
+                {
+                    var gap = Math.Max(0, item.Number - (end + 1));
+                    var aligned = (item.Number - start) % width == 0;
+                    var newEnd = Math.Max(end, itemEnd);
+                    // The span check is on the ROUNDED length a flush would produce.
+                    var roundedSpan = (newEnd - start + 1 + width - 1) / width * width;
+                    if (aligned && gap <= maxGapBytes && roundedSpan <= maxSpanBytes)
+                    {
+                        members.Add(item);
+                        end = newEnd;
+                        continue;
+                    }
+                    Flush();
+                }
+                members = [item];
+                start = item.Number;
+                end = itemEnd;
+            }
+            Flush();
+        }
+        return plans;
+    }
+
+    /// <summary>The data type whose wire width a read of <paramref name="type"/> uses (Bit and Byte share one).</summary>
+    /// <param name="type">The tag's declared type.</param>
+    /// <returns>The representative slot type.</returns>
+    public static FocasDataType SlotTypeOf(FocasDataType type) => type switch
+    {
+        FocasDataType.Bit or FocasDataType.Byte => FocasDataType.Byte,
+        _ => type,
+    };
+
+    /// <summary>
+    ///     Decodes one raw PMC slot (as <c>pmc_rdpmcrng</c> parsed it) into the tag's published value. The single
+    ///     decode authority for both the per-tag and the coalesced path.
+    /// </summary>
+    /// <param name="raw">The slot value.</param>
+    /// <param name="type">The tag's declared type.</param>
+    /// <param name="bitIndex">Bit index for a Bit tag.</param>
+    /// <returns>The boxed value.</returns>
+    public static object MapSlot(long raw, FocasDataType type, int? bitIndex) => type switch
+    {
+        FocasDataType.Bit => (object)(((raw >> (bitIndex ?? 0)) & 1L) != 0),
+        FocasDataType.Byte => (object)(sbyte)(raw & 0xFFL),
+        FocasDataType.Int16 => (object)(short)raw,
+        FocasDataType.Int32 => (object)(int)raw,
+        FocasDataType.Float32 => (object)BitConverter.Int32BitsToSingle((int)raw),
+        FocasDataType.Float64 => (object)BitConverter.Int64BitsToDouble(raw),
+        _ => (object)raw,
+    };
+}

src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.FOCAS/IFocasClient.cs

@@ -73,6 +73,24 @@ public interface IFocasClient : IDisposable
     /// <returns>The list of currently active alarms; empty when none are active.</returns>
     Task<IReadOnlyList<FocasActiveAlarm>> ReadAlarmsAsync(CancellationToken cancellationToken);
 
+    /// <summary>
+    ///     Read one PMC range (<c>pmc_rdpmcrng</c>) as raw slots: <c>(end - start + 1)</c> bytes split into
+    ///     slots of <paramref name="slotType"/>'s width, from <paramref name="start"/>. The primitive behind PMC
+    ///     range coalescing (Gitea #266) — the driver slices individual tag values out of the returned slots with
+    ///     the same decode a per-tag read uses.
+    /// </summary>
+    /// <param name="letter">PMC area letter.</param>
+    /// <param name="slotType">Decides the slot width (Bit/Byte = 1, Int16 = 2, Int32/Float32 = 4, Float64 = 8).</param>
+    /// <param name="start">First byte address.</param>
+    /// <param name="end">Last byte address, inclusive; a whole number of slots from <paramref name="start"/>.</param>
+    /// <param name="cancellationToken">The cancellation token.</param>
+    /// <returns>
+    ///     The raw slot values (null when not Good) and the mapped OPC UA status. A returned non-Good status is
+    ///     always a CNC return-code refusal; a transport failure or timeout throws instead.
+    /// </returns>
+    Task<(IReadOnlyList<long>? slots, uint status)> ReadPmcSlotsAsync(
+        string letter, FocasDataType slotType, int start, int end, CancellationToken cancellationToken);
+
     // ---- Fixed-tree T1 (identity + axis discovery + fast-poll dynamic bundle) ----
 
     /// <summary>
@@ -125,6 +143,17 @@ public interface IFocasClient : IDisposable
     /// <returns>The aggregate program + operation-mode snapshot.</returns>
     Task<FocasProgramInfo> GetProgramInfoAsync(CancellationToken cancellationToken);
 
+    // ---- Fixed-tree T2.5 (CNC status flags, Gitea #257) ----
+
+    /// <summary>
+    ///     Read the CNC status flags via <c>cnc_statinfo</c> (<c>ODBST</c>). Populates the
+    ///     <c>Status/*</c> subtree. Throws when the CNC refuses the call, which the driver's
+    ///     bootstrap probe reads as "this series has no status block" and suppresses the subtree.
+    /// </summary>
+    /// <param name="cancellationToken">The cancellation token.</param>
+    /// <returns>The CNC status flag snapshot.</returns>
+    Task<FocasStatus> GetStatusAsync(CancellationToken cancellationToken);
+
     // ---- Fixed-tree T3 (timers) ----
 
     /// <summary>
@@ -172,6 +201,38 @@ public interface IFocasClient : IDisposable
     Task<IReadOnlyList<double?>> GetSpindleMotorSpeedsAsync(CancellationToken cancellationToken);
 }
 
+/// <summary>
+///     CNC status flags from <c>cnc_statinfo</c> (<c>ODBST</c>) — raw FANUC codes, published verbatim as
+///     Int32 so a client sees exactly what the control reported. <see cref="Run"/> additionally has a
+///     text projection (<see cref="FocasRunState.ToText"/>).
+/// </summary>
+/// <param name="Auto">Automatic-operation mode code.</param>
+/// <param name="Run">Automatic-operation state (0 RESET, 1 STOP, 2 HOLD, 3 START, 4 MSTR).</param>
+/// <param name="Motion">Axis motion (0 none, 1 motion, 2 dwell).</param>
+/// <param name="Mstb">M/S/T/B function state (0 none, 1 executing).</param>
+/// <param name="Emergency">Emergency stop (0 not, 1 emergency, 2 reset).</param>
+/// <param name="Alarm">Alarm state (0 none, 1 alarm, 2 battery-low, 3 fan).</param>
+/// <param name="Edit">Program-edit state.</param>
+/// <param name="TmMode">T/M mode as reported by the control.</param>
+public sealed record FocasStatus(int Auto, int Run, int Motion, int Mstb, int Emergency, int Alarm, int Edit, int TmMode);
+
+/// <summary>Human-readable text for <see cref="FocasStatus.Run"/>.</summary>
+public static class FocasRunState
+{
+    /// <summary>Converts the <c>ODBST.run</c> code to its operator-facing label.</summary>
+    /// <param name="run">The run-state code.</param>
+    /// <returns>The label, or <c>Run{n}</c> for a code outside the documented set.</returns>
+    public static string ToText(int run) => run switch
+    {
+        0 => "RESET",
+        1 => "STOP",
+        2 => "HOLD",
+        3 => "START",
+        4 => "MSTR",
+        _ => $"Run{run}",
+    };
+}
+
 /// <summary>
 ///     One servo-meter entry — one axis's current load percentage; null when the CNC's record
 ///     described no usable value (never a fabricated 0).

src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.FOCAS/SynchronizedFocasClient.cs

@@ -61,6 +61,11 @@ public sealed class SynchronizedFocasClient : IFocasClient
         FocasAddress address, FocasDataType type, CancellationToken cancellationToken) =>
         RunBoundedAsync(ct => _inner.ReadAsync(address, type, ct), cancellationToken);
 
+    /// <inheritdoc />
+    public Task<(IReadOnlyList<long>? slots, uint status)> ReadPmcSlotsAsync(
+        string letter, FocasDataType slotType, int start, int end, CancellationToken cancellationToken) =>
+        RunBoundedAsync(ct => _inner.ReadPmcSlotsAsync(letter, slotType, start, end, ct), cancellationToken);
+
     /// <inheritdoc />
     public Task<uint> WriteAsync(
         FocasAddress address, FocasDataType type, object? value, CancellationToken cancellationToken) =>
@@ -90,6 +95,10 @@ public sealed class SynchronizedFocasClient : IFocasClient
     public Task<FocasProgramInfo> GetProgramInfoAsync(CancellationToken cancellationToken) =>
         RunBoundedAsync(ct => _inner.GetProgramInfoAsync(ct), cancellationToken);
 
+    /// <inheritdoc />
+    public Task<FocasStatus> GetStatusAsync(CancellationToken cancellationToken) =>
+        RunBoundedAsync(ct => _inner.GetStatusAsync(ct), cancellationToken);
+
     /// <inheritdoc />
     public Task<FocasTimer> GetTimerAsync(FocasTimerKind kind, CancellationToken cancellationToken) =>
         RunBoundedAsync(ct => _inner.GetTimerAsync(kind, ct), cancellationToken);

src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.FOCAS/Wire/WireFocasClient.cs

@@ -67,6 +67,33 @@ public sealed class WireFocasClient : IFocasClient
         };
     }
 
+    /// <inheritdoc />
+    public async Task<(IReadOnlyList<long>? slots, uint status)> ReadPmcSlotsAsync(
+        string letter, FocasDataType slotType, int start, int end, CancellationToken cancellationToken)
+    {
+        // Contract: a RETURNED status is always a CNC return code (a refusal); a transport failure THROWS.
+        // The coalescing caller needs that distinction — it falls back per tag on a refusal but must not
+        // re-hit a dead link (#266).
+        RequireConnected();
+        cancellationToken.ThrowIfCancellationRequested();
+
+        var area = FocasPmcAreaLookup.FromLetter(letter);
+        if (area is null) return (null, FocasStatusMapper.BadNodeIdUnknown);
+        var dataType = FocasPmcDataTypeLookup.FromFocasDataType(slotType);
+        try
+        {
+            var result = await _wire.ReadPmcRangeAsync(area.Value, dataType, (ushort)start, (ushort)end, cancellationToken)
+                .ConfigureAwait(false);
+            if (!result.IsOk || result.Value is null)
+                return (null, FocasStatusMapper.MapFocasReturn(result.Rc));
+            return (result.Value.Values, FocasStatusMapper.Good);
+        }
+        catch (FocasWireException ex) when (ex.Rc is short rc)
+        {
+            return (null, FocasStatusMapper.MapFocasReturn(rc));
+        }
+    }
+
     /// <inheritdoc />
     public Task<uint> WriteAsync(
         FocasAddress address, FocasDataType type, object? value, CancellationToken cancellationToken)
@@ -129,6 +156,18 @@ public sealed class WireFocasClient : IFocasClient
             AxesCount: axesCount);
     }
 
+    /// <inheritdoc />
+    public async Task<FocasStatus> GetStatusAsync(CancellationToken cancellationToken)
+    {
+        RequireConnected();
+        var result = await _wire.ReadStatusAsync(cancellationToken).ConfigureAwait(false);
+        ThrowIfRcNonZero(result.Rc, "cnc_statinfo", result.IsOk);
+        return MapStatus(result.Value!);
+    }
+
+    internal static FocasStatus MapStatus(WireStatus s) =>
+        new(s.Auto, s.Run, s.Motion, s.Mstb, s.Emergency, s.Alarm, s.Edit, s.TmMode);
+
     /// <inheritdoc />
     public async Task<IReadOnlyList<FocasAxisName>> GetAxisNamesAsync(CancellationToken cancellationToken)
     {
@@ -313,17 +352,8 @@ public sealed class WireFocasClient : IFocasClient
                 return (null, FocasStatusMapper.MapFocasReturn(result.Rc));
             var values = result.Value.Values;
             if (values.Count == 0) return (null, FocasStatusMapper.BadOutOfRange);
-            var raw = values[0];
-            var mapped = type switch
-            {
-                FocasDataType.Bit => (object)(((long)raw >> (address.BitIndex ?? 0) & 1L) != 0),
-                FocasDataType.Byte => (object)(sbyte)(raw & 0xFFL),
-                FocasDataType.Int16 => (object)(short)raw,
-                FocasDataType.Int32 => (object)(int)raw,
-                FocasDataType.Float32 => (object)BitConverter.Int32BitsToSingle((int)raw),
-                FocasDataType.Float64 => (object)BitConverter.Int64BitsToDouble(raw),
-                _ => (object)raw,
-            };
+            // One decode authority shared with the coalesced path (FocasPmcCoalescer.MapSlot).
+            var mapped = FocasPmcCoalescer.MapSlot(values[0], type, address.BitIndex);
             return (mapped, FocasStatusMapper.Good);
         }
         catch (FocasWireException ex)