Gotchas

Symptom: Timer/counter preset write returns E1

Root cause	Fix
Timer/counter preset write commands are supported on KV-8000/7000-series, not on KV-3000, KV-5000, or KV-NANO.	Read timer/counter values with the helper API, and do not write presets on unsupported models.

using System;
using PlcComm.KvHostLink;

var options = new KvHostLinkConnectionOptions("192.168.250.100", 8501);
await using var client = await KvHostLinkClientFactory.OpenAndConnectAsync(options);

KvTimerCounterValue timer = await client.ReadTimerAsync("T0");
Console.WriteLine($"T0 status={timer.Status}, current={timer.Current}, preset={timer.Preset}");

Symptom: AT device fails on KV-X500

Root cause	Fix
AT digital trimmer devices are not available in KV-X500 profiles.	Check the selected profile catalog before reading AT.

using System;
using PlcComm.KvHostLink;

var catalog = KvHostLinkDeviceRanges.DeviceRangeCatalogForPlcProfile("keyence:kv-x500");
var at = catalog.Entry("AT");
Console.WriteLine($"AT supported: {at?.Supported == true}");

Symptom: X or Y address is rejected

Root cause	Fix
X and Y use decimal-bank plus hex-bit notation.	Use an address such as X10F, where 10 is the bank and F is the bit.

using System;
using PlcComm.KvHostLink;

Console.WriteLine(KvHostLinkAddress.Normalize("X10F"));

Symptom: R, MR, LR, or CR address is rejected

Root cause	Fix
These bit families use two-digit bit notation, not a plain hexadecimal number.	Use forms such as R200 or MR100.

using System;
using PlcComm.KvHostLink;

Console.WriteLine(KvHostLinkAddress.Normalize("MR100"));

Symptom: Connection fails immediately

Root cause	Fix
KV Host Link examples use port 8501, not 1025.	Set port 8501 unless your PLC connection node is configured differently.

using PlcComm.KvHostLink;

var options = new KvHostLinkConnectionOptions("192.168.250.100", 8501);
await using var client = await KvHostLinkClientFactory.OpenAndConnectAsync(options);

Symptom: Non-canonical profile string fails immediately

Root cause	Fix
Device range catalog selection accepts only exact canonical profile strings from source.	Copy one exact string from PLC profiles.

using System;
using PlcComm.KvHostLink;

var catalog = KvHostLinkDeviceRanges.DeviceRangeCatalogForPlcProfile("keyence:kv-7000");
Console.WriteLine(catalog.PlcProfile);

Symptom: Expansion unit buffer read fails

Root cause	Fix
The selected unit number, buffer address, data format, or module may not match your connected PLC hardware.	Verify the expansion unit number and buffer address before calling the buffer API.

using System;
using PlcComm.KvHostLink;

var options = new KvHostLinkConnectionOptions("192.168.250.100", 8501);
await using var client = await KvHostLinkClientFactory.OpenAndConnectAsync(options);

string[] values = await client.ReadExpansionUnitBufferAsync(
    unitNo: 0,
    address: 0,
    count: 4,
    dataFormat: ".U");

Console.WriteLine($"Read {values.Length} values.");