Phase 3 PR 51 -- DL260 X-input FC02 discrete-input mapping end-to-end test. Integration test DL205XInputTests reads FC02 at the DirectLogicAddress.XInputToDiscrete-resolved address and asserts two behaviors against the dl205.json pymodbus profile: (1) X20 octal (=decimal 16 = Modbus DI 16) reads ON, proving the helper correctly octal-parses the trailing number and adds it to the 0 base; (2) X21 octal reads OFF (not exception) -- per docs/v2/dl205.md §I/O-mapping, 'reading a non-populated X input returns zero, not an exception' on DL260, because the CPU sizes the discrete-input table to the configured I/O not the installed hardware. Pymodbus models this by returning the default 0 value for any DI bit in the configured 'di size' range that wasn't explicitly seeded, matching real DL260 behaviour. Test uses X20 rather than X0 to sidestep a shared-blocks conflict: pymodbus places FC01/FC02 bit-address 0..15 into cell 0, but cell 0 is already uint16-typed (V0 marker = 0xCAFE) per the register-zero quirk test, and shared-blocks semantics allow only one type per cell. X20 octal = DI 16 lands in cell 1 which is free, so both the V0 quirk AND the X-input quirk can coexist in one profile. dl205.json: bits cell 1 seeded value=9 (bits 0 and 3 set -> X20, X23 octal = ON), write-range extended to include cell 1 (though X-inputs are read-only; the write-range entry is required by pymodbus for ANY cell referenced in a bits section even if only reads are expected -- pymodbus validates write-access uniformly). 10/10 DL205 integration tests pass with MODBUS_SIM_PROFILE=dl205. No driver code changes -- the XInputToDiscrete helper + FC02 read path already landed in PRs 50 and 21 respectively. This PR closes the integration-test gap that docs/v2/dl205.md called out under test name DL205_Xinput_unpopulated_reads_as_zero.

tests/ZB.MOM.WW.OtOpcUa.Driver.Modbus.IntegrationTests/DL205/DL205XInputTests.cs

@@ -0,0 +1,71 @@
+using Shouldly;
+using Xunit;
+
+namespace ZB.MOM.WW.OtOpcUa.Driver.Modbus.IntegrationTests.DL205;
+
+/// <summary>
+///     Verifies the DL260 X-input discrete-input mapping against the <c>dl205.json</c>
+///     pymodbus profile. X-inputs are FC02 discrete-input-only (Modbus doesn't allow writes
+///     to discrete inputs), and the DirectLOGIC convention is X0 → DI 0 with octal offsets
+///     for subsequent addresses. The sim seeds X20 octal (= DI 16) = ON so the test can
+///     prove the helper routes through to the right cell.
+/// </summary>
+/// <remarks>
+///     X0 / X1 / …X17 octal all share cell 0 (DI 0-15 → cell 0 bits 0-15) which conflicts
+///     with the V0 uint16 marker; we can't seed both types at cell 0 under shared-blocks
+///     semantics. So the test uses X20 octal (first address beyond the cell-0 boundary) which
+///     lands cleanly at cell 1 bit 0 and leaves the V0 register-zero quirk intact.
+/// </remarks>
+[Collection(ModbusSimulatorCollection.Name)]
+[Trait("Category", "Integration")]
+[Trait("Device", "DL205")]
+public sealed class DL205XInputTests(ModbusSimulatorFixture sim)
+{
+    [Fact]
+    public async Task DL260_X20_octal_maps_to_DiscreteInput_16_and_reads_ON()
+    {
+        if (sim.SkipReason is not null) Assert.Skip(sim.SkipReason);
+        if (!string.Equals(Environment.GetEnvironmentVariable("MODBUS_SIM_PROFILE"), "dl205",
+                StringComparison.OrdinalIgnoreCase))
+        {
+            Assert.Skip("MODBUS_SIM_PROFILE != dl205 — skipping.");
+        }
+
+        // X20 octal = decimal 16 = DI 16 per the DL260 convention (X-inputs start at DI 0).
+        var di = DirectLogicAddress.XInputToDiscrete("X20");
+        di.ShouldBe((ushort)16);
+
+        var options = BuildOptions(sim, [
+            new ModbusTagDefinition("DL260_X20",
+                ModbusRegion.DiscreteInputs, Address: di,
+                DataType: ModbusDataType.Bool, Writable: false),
+            // Unpopulated-X control: pymodbus returns 0 (not exception) for any bit in the
+            // configured DI range that wasn't explicitly seeded — per docs/v2/dl205.md
+            // "Reading a non-populated X input ... returns zero, not an exception".
+            new ModbusTagDefinition("DL260_X21_off",
+                ModbusRegion.DiscreteInputs, Address: DirectLogicAddress.XInputToDiscrete("X21"),
+                DataType: ModbusDataType.Bool, Writable: false),
+        ]);
+        await using var driver = new ModbusDriver(options, driverInstanceId: "dl205-xinput");
+        await driver.InitializeAsync("{}", TestContext.Current.CancellationToken);
+
+        var results = await driver.ReadAsync(["DL260_X20", "DL260_X21_off"], TestContext.Current.CancellationToken);
+
+        results[0].StatusCode.ShouldBe(0u);
+        results[0].Value.ShouldBe(true, "dl205.json seeds cell 1 bit 0 (X20 octal = DI 16) = ON");
+
+        results[1].StatusCode.ShouldBe(0u, "unpopulated X inputs must read cleanly — DL260 does NOT raise an exception");
+        results[1].Value.ShouldBe(false);
+    }
+
+    private static ModbusDriverOptions BuildOptions(ModbusSimulatorFixture sim, IReadOnlyList<ModbusTagDefinition> tags)
+        => new()
+        {
+            Host = sim.Host,
+            Port = sim.Port,
+            UnitId = 1,
+            Timeout = TimeSpan.FromSeconds(2),
+            Tags = tags,
+            Probe = new ModbusProbeOptions { Enabled = false },
+        };
+}

tests/ZB.MOM.WW.OtOpcUa.Driver.Modbus.IntegrationTests/Pymodbus/dl205.json

@@ -36,6 +36,7 @@
         [1280, 1282],
         [1343, 1343],
         [1407, 1407],
+        [1, 1],
         [128, 128],
         [192, 192],
         [250, 250],
@@ -88,6 +89,9 @@
       ],
 
       "bits": [
+        {"_quirk": "X-input bank marker cell. X0 -> DI 0 conflicts with uint16 V0 at cell 0, so this marker covers X20 octal (= decimal 16 = DI 16 = cell 1 bit 0). X20=ON, X23 octal (DI 19 = cell 1 bit 3)=ON -> cell 1 value = 0b00001001 = 9.",
+         "addr": 1, "value": 9},
+
         {"_quirk": "Y-output bank marker cell. pymodbus's simulator maps Modbus FC01/02/05 bit-addresses to cell index = bit_addr / 16; so Modbus coil 2048 lives at cell 128 bit 0. Y0=ON (bit 0), Y1=OFF (bit 1), Y2=ON (bit 2) -> value=0b00000101=5 proves DL260 mapping Y0 -> coil 2048.",
          "addr": 128, "value": 5},