Weintek cMT — 'PLC No Response' Communication Fix

Weintek · intermediate · 25 min

A Weintek 'PLC No Response' is a network-layer failure — the HMI can't reach the PLC, not a tag error. Check IP/subnet, protocol variant, and poll cycle, and use cMT Diagnoser to pinpoint it.

ℹ️ 'PLC No Response' means the HMI is not getting an answer at the communication layer — a wiring, addressing, or protocol problem. It is not a tag or address-mapping error, so start at the network, not the tag list.

What 'PLC No Response' means

On a Weintek cMT HMI, a PLC No Response (or device 'no response') message is a network-layer / hardware-level communication failure — the HMI cannot reach the PLC at the communication layer. Importantly, this is not a tag or addressing error; the panel isn't getting any answer at all, so the fix lives in the connection, addressing, and protocol settings.

Work the causes in order

1. IP / subnet (Ethernet). A static IP must be defined, and the HMI's IP must be on the same subnet as the PLC. Set the HMI network in the on-panel Network menu (log in to reveal the configuration tabs). Wrong IP/subnet is the most common Ethernet cause.
2. Protocol variant. Using the wrong protocol variant for the PLC causes a NO RESPONSE — confirm the driver in EasyBuilder Pro exactly matches the PLC family and protocol (e.g. the correct Modbus TCP/RTU or vendor-specific driver).
3. Serial parameters (RS-232/485). For serial links, verify baud, parity, stop bits, and the station/unit address, and the correct COM port and wiring.
4. Poll cycle timing. A ~10-second response delay is a classic symptom of a misconfigured Poll Cycle — check System Parameters → Device → Poll Cycle in EasyBuilder to correct sluggish or timed-out polling.
5. Software version. Some no-response cases are resolved by updating EasyBuilder Pro (e.g. a fix between minor versions) — use a current EasyBuilder Pro build.
6. Tag database mismatch. If comms work but some values are wrong, the HMI tag library may reference addresses the PLC doesn't map — align the tags to the PLC's actual memory map (this is a value issue, distinct from a true no-response).

Use cMT Diagnoser

Weintek's cMT Diagnoser was built for exactly this — on cMT-series HMIs and Gateways it gives an overview of device behavior and helps find the cause of an operation/communication error quickly. Run it to see live device status and which device isn't answering.

Step-by-step

1. Ethernet: confirm the HMI has a static IP on the PLC's subnet (Network menu).
2. Driver: verify the exact protocol variant matches the PLC in EasyBuilder Pro.
3. Serial: check baud/parity/stop/address and COM port/wiring.
4. Poll cycle: correct System Parameters → Device → Poll Cycle if responses are slow/timing out.
5. cMT Diagnoser: run it to pinpoint the failing device.
6. Re-download the project after changes and confirm the no-response clears.

Verify

Once corrected, the device answers and tags update live. If 'PLC No Response' persists after IP/subnet and protocol are confirmed, re-check the physical layer (cable/switch/port) and the PLC-side settings.