Gotchas

LTN/LSTN/LCN/LZ returns wrong values

Item	Detail
Symptom	Long timer, long counter, or long index values look truncated or shifted.
Root cause	LTN, LSTN, LCN, and LZ are 32-bit logical families.
Fix	Use :D or :L in named addresses, or pass D or L to ReadTypedAsync.

using System;
using PlcComm.Slmp;

var options = new SlmpConnectionOptions("192.168.250.100", SlmpPlcProfile.IqR)
{
    Port = 1025,
};

await using var client = await SlmpClientFactory.OpenAndConnectAsync(options);
var value = await client.ReadTypedAsync("LTN0", "D");
Console.WriteLine($"LTN0 = {value}");

LCS/LCC reads incorrect

Item	Detail
Symptom	Long counter state reads do not match the expected contact or coil state.
Root cause	LCS and LCC are state bits; they are not 16-bit word current values.
Fix	Read them as bit values and let WriteTypedAsync / WriteNamedAsync route writes through random bit write.

using System;
using PlcComm.Slmp;

var options = new SlmpConnectionOptions("192.168.250.100", SlmpPlcProfile.IqR)
{
    Port = 1025,
};

await using var client = await SlmpClientFactory.OpenAndConnectAsync(options);
var state = await client.ReadTypedAsync("LCS0", "BIT");
await client.WriteTypedAsync("LCC0", "BIT", true);
Console.WriteLine($"LCS0 = {state}");

LTS/LTC/LSTS/LSTC write rejected

Item	Detail
Symptom	Writing a long timer contact or coil through a normal direct bit route is rejected.
Root cause	Long timer state writes use SLMP random bit write, not ordinary direct bit write.
Fix	Use WriteTypedAsync or WriteNamedAsync so the library selects the correct route.

using System;
using System.Collections.Generic;
using PlcComm.Slmp;

var options = new SlmpConnectionOptions("192.168.250.100", SlmpPlcProfile.IqR)
{
    Port = 1025,
};

await using var client = await SlmpClientFactory.OpenAndConnectAsync(options);
await client.WriteTypedAsync("LTC0", "BIT", true);
var state = await client.ReadTypedAsync("LTC0", "BIT");
Console.WriteLine($"LTC0 = {state}");

G/HG fails

Item	Detail
Symptom	G or HG fails in the high-level typed or named API.
Root cause	Module buffer memory is outside the public high-level device surface.
Fix	Use low-level module-buffer APIs on the raw SlmpClient when you need module buffer access.

using System;
using System.Threading.Tasks;
using PlcComm.Slmp;

await using var raw = new SlmpClient("192.168.250.100", SlmpPlcProfile.IqR, port: 1025);
await raw.OpenAsync();

var device = SlmpQualifiedDeviceParser.Parse(@"U3\G100");
var extension = new SlmpExtensionSpec();
ushort[] words = await raw.ReadWordsExtendedAsync(device, points: 4, extension);
Console.WriteLine($"G100 words = {words.Length}");

Mixed write fails

Item	Detail
Symptom	One mixed write containing word values and bit values fails.
Root cause	The PLC rejects SLMP command 0x1406 for a mixed word and bit request.
Fix	Send word writes and bit writes as separate calls.

using System;
using PlcComm.Slmp;

var options = new SlmpConnectionOptions("192.168.250.100", SlmpPlcProfile.IqR)
{
    Port = 1025,
};

await using var client = await SlmpClientFactory.OpenAndConnectAsync(options);
await client.WriteNamedAsync(new Dictionary<string, object>
{
    ["D9000"] = (ushort)1234,
});
await client.WriteNamedAsync(new Dictionary<string, object>
{
    ["M9000"] = true,
});
Console.WriteLine("Separated word and bit writes.");

DX/DY fails on iQ-F

Item	Detail
Symptom	DX or DY is rejected when the selected profile is SlmpPlcProfile.IqF.
Root cause	iQ-F profile rules do not support DX and DY.
Fix	Use X and Y with the iQ-F profile.

using System;
using PlcComm.Slmp;

var parsed = SlmpAddress.Parse("X20", SlmpPlcProfile.IqF);
Console.WriteLine(SlmpAddress.Format(parsed, SlmpPlcProfile.IqF));

All reads return end code

Item	Detail
Symptom	The connection opens, but every read returns an SLMP end-code error.
Root cause	The selected SlmpPlcProfile does not match the actual PLC hardware.
Fix	Choose the profile that matches the PLC; the profile determines frame type and compatibility mode.

using System;
using PlcComm.Slmp;

var options = new SlmpConnectionOptions("192.168.250.100", SlmpPlcProfile.IqR)
{
    Port = 1025,
};

await using var client = await SlmpClientFactory.OpenAndConnectAsync(options);
Console.WriteLine($"{client.FrameType} {client.CompatibilityMode}");

SlmpPlcProfile.Unspecified throws immediately

Item	Detail
Symptom	Creating connection options or resolving defaults with SlmpPlcProfile.Unspecified fails before any PLC request.
Root cause	Unspecified is not a concrete PLC profile and cannot select frame type or compatibility mode.
Fix	Use a concrete .NET selector such as SlmpPlcProfile.IqR.

using System;
using PlcComm.Slmp;

try
{
    _ = SlmpPlcProfiles.Resolve(SlmpPlcProfile.Unspecified);
}
catch (ArgumentOutOfRangeException)
{
    var defaults = SlmpPlcProfiles.Resolve(SlmpPlcProfile.IqR);
    Console.WriteLine($"{defaults.FrameType} {defaults.CompatibilityMode}");
}

Concurrent callers crash

Item	Detail
Symptom	Multiple async callers using one raw SlmpClient cause overlapping requests or inconsistent responses.
Root cause	Raw SlmpClient is not thread-safe for concurrent callers.
Fix	Use the QueuedSlmpClient returned by SlmpClientFactory.OpenAndConnectAsync.

using System;
using PlcComm.Slmp;

var options = new SlmpConnectionOptions("192.168.250.100", SlmpPlcProfile.IqR)
{
    Port = 1025,
};

await using var client = await SlmpClientFactory.OpenAndConnectAsync(options);
var first = client.ReadTypedAsync("D100", "U");
var second = client.ReadTypedAsync("D101", "U");
var values = await Task.WhenAll(first, second);
Console.WriteLine($"{values[0]}, {values[1]}");

X or Y addresses do not match an iQ-F manual

Item	Detail
Symptom	X or Y addresses look shifted on iQ-F.
Root cause	iQ-F uses octal notation for X and Y; other supported profiles use hexadecimal.
Fix	Parse or normalize X and Y with the explicit iQ-F profile.

using System;
using PlcComm.Slmp;

var address = SlmpAddress.Parse("Y217", SlmpPlcProfile.IqF);
Console.WriteLine(SlmpAddress.Format(address, SlmpPlcProfile.IqF));