Gotchas

Timer/counter preset write returns E1

Field	Detail
Symptom	A timer or counter preset write returns E1.
Root cause	Host Link preset writes through WS and WSS are supported on KV-8000/7000-series, not on KV-3000, KV-5000, or KV-NANO.
Fix	Do not write timer/counter presets on unsupported models; use read_timer, read_counter, or read_timer_counter for safe reads.

use plc_comm_hostlink::{HostLinkClient, HostLinkConnectionOptions};

#[tokio::main]
async fn main() -> Result<(), Box<dyn std::error::Error>> {
    let client =
        HostLinkClient::connect(HostLinkConnectionOptions::new("192.168.250.100")).await?;

    let value = client.read_timer_counter("T0").await?;
    println!("{:?}", value);

    client.close().await?;
    Ok(())
}

AT device fails on KV-X500

Field	Detail
Symptom	Reading AT0 fails or the range catalog reports no AT entry for KV-X500.
Root cause	AT is not available in keyence:kv-x500 or keyence:kv-x500-xym.
Fix	Check the selected profile before using AT, and avoid AT on KV-X500 projects.

use plc_comm_hostlink::device_range_catalog_for_plc_profile;

fn main() -> Result<(), Box<dyn std::error::Error>> {
    let catalog = device_range_catalog_for_plc_profile("keyence:kv-x500")?;
    println!("{:?}", catalog.entry("AT"));
    Ok(())
}

X or Y address rejected

Field	Detail
Symptom	X or Y raises an address parse or PLC device-number error.
Root cause	X and Y use decimal-bank plus hex-bit notation. X10F means bank 10, bit F.
Fix	Use X10F or Y10F, and select an -xym profile when you want XYM aliases.

use plc_comm_hostlink::HostLinkAddress;

fn main() -> Result<(), Box<dyn std::error::Error>> {
    let address = HostLinkAddress::normalize("X10F")?;
    println!("{address}");
    Ok(())
}

R, MR, LR, or CR address rejected

Field	Detail
Symptom	R, MR, LR, or CR raises an address parse or PLC device-number error.
Root cause	These families use KEYENCE two-digit bit notation.
Fix	Use forms such as R200 or MR100; do not treat the full suffix as one hexadecimal number.

use plc_comm_hostlink::HostLinkAddress;

fn main() -> Result<(), Box<dyn std::error::Error>> {
    let address = HostLinkAddress::normalize("MR100")?;
    println!("{address}");
    Ok(())
}

Wrong port causes an immediate timeout

Field	Detail
Symptom	The connection times out immediately even though the PLC responds on the network.
Root cause	KV Host Link uses port 8501, not the SLMP/Computerlink port 1025.
Fix	Set options.port = 8501 or leave the default from HostLinkConnectionOptions::new.

use plc_comm_hostlink::HostLinkConnectionOptions;

fn main() {
    let mut options = HostLinkConnectionOptions::new("192.168.250.100");
    options.port = 8501;
    println!("{}", options.port);
}

Non-canonical profile string rejected

Field	Detail
Symptom	A display label, uppercase variant, or old alias returns HostLinkError.
Root cause	The range catalog accepts only exact canonical profile strings. It does not infer the profile from a PLC model response.
Fix	Store the canonical string from PROFILES.md in your project settings or UI value.

use plc_comm_hostlink::available_plc_profiles;

fn main() {
    for profile in available_plc_profiles() {
        println!("{profile}");
    }
}

DM100.D reads the wrong thing

Field	Detail
Symptom	DM100.D reads a boolean-like value instead of a 32-bit value.
Root cause	Dot notation means bit-in-word, so DM100.D is bit 13, not a double-word read.
Fix	Use the dtype argument or colon notation for data types.

use plc_comm_hostlink::{HostLinkClient, HostLinkConnectionOptions};

#[tokio::main]
async fn main() -> Result<(), Box<dyn std::error::Error>> {
    let client =
        HostLinkClient::connect(HostLinkConnectionOptions::new("192.168.250.100")).await?;

    let value = client.read_typed("DM100", "D").await?;
    println!("{:?}", value);

    client.close().await?;
    Ok(())
}

CTH or CTC address rejected

Field	Detail
Symptom	CTH or CTC appears in the catalog but fails as an input address.
Root cause	CTH and CTC are catalog metadata rows for supported profiles, while the current address parser does not accept them as input addresses.
Fix	Treat them as catalog metadata only.

use plc_comm_hostlink::device_range_catalog_for_plc_profile;

fn main() -> Result<(), Box<dyn std::error::Error>> {
    let catalog = device_range_catalog_for_plc_profile("keyence:kv-5000")?;
    println!("{:?}", catalog.entry("CTH"));
    Ok(())
}