Host Link devices and point limits (KV-8000 / 7000 / 5000 / Nano)

The devices and number ranges available over Host Link depend on the PLC model, and each command has a limit on how many points it can read or write at once. This article summarizes both from the manual’s tables.

Devices and number ranges

• *1 00000–99915 via the KV-EP21V, or on a KV-7000 with CPU function version 2.2 or earlier
• *2 00000–99915 via the KV-EP21V
• *3 On the KV Nano it depends on the base unit (KV-NC32T: CTH0–2 / CTC0–5, KV-N24: CTH0–1 / CTC0–3, and so on)

R, MR, LR and CR are written as “channel + two-digit bit number”; B, VB and W are hexadecimal (see the format article).

Points per RDS / WRS

The count of RDS and WRS has a limit. With the 32-bit formats (.D / .L), the limit is roughly halved.

Limits of other commands

The devices you can register for monitoring depend on the command:

• MBS (bits): R, B, MR, LR, CR, T, C, CTC (contacts), VB
• MWS (words): R, B, MR, LR, CR, VB, DM, EM, FM, ZF, W, TM, Z, TC, TS, CC, CS, AT, CM, VM (plus CTH and CTC on the KV-5500 and KV Nano)

When registering relays with MWS, specify them per channel (the first bit of the channel).

Force set / reset (ST / RS) works on R, B, MR, LR, CR, T, C, CTC and VB, with CTC accepting only RS. Continuous force set / reset (STS / RSS) works on R, B, MR, LR, CR and VB.

KcpX splits requests that exceed the limit

In KcpX, you give the model as a PlcSeries when you connect. KcpX works out the limit from the model, the device and the type, and splits anything beyond it into several commands.

using var kcpx = new KcpX("192.168.0.10", 8501, series: PlcSeries.KV7000);

// Read as three RDS commands of 1000 points
bool[] mr = kcpx.BatchRead<bool>(Prefix.MR, "0", 3000);

// int is .L, so write as two WRS commands of 500 points
kcpx.BatchWrite<int>(Prefix.DM, "1000", new int[1000]);

// More than 16 points, so send STS twice
kcpx.BatchForceSet(Prefix.MR, "1000", 20);

KcpX does not check number ranges itself; it leaves that to the PLC. An out-of-range number makes the PLC return E0, which raises a HostLinkException (see the error response article).