Resolving NS5-SQ11B-V2 to CJ2M-CPU33 Direct Ethernet Link Down

Problem Definition

When a brand-new NS5-SQ11B-V2 HMI is connected directly to a CJ2M-CPU33 with its built-in Ethernet port, the most common field symptom is: both devices work independently when attached to a PC or office network, but the moment a single patch cable is run between them, the HMI raises a Communication Timeout or Host Not Found error and the LINK/ACT LEDs on the CJ2M-CPU33 stay dark. Because both endpoints ping from a laptop, the operating engineer naturally assumes the cable and the IP plan are good — yet the link never comes up.

This document walks through the six most likely root causes, in the order they should be ruled out on the bench, and the exact commissioning sequence that brings the link up reliably on a direct (point-to-point) connection.

Hardware Reference and Network Fundamentals

The CJ2M-CPU33 is a CJ2M-series CPU unit with an integrated 10/100Base-TX Ethernet port on the front of the module. The port supports CIP (EtherNet/IP), FINS/UDP, FINS/TCP, and socket services. See the CJ2M CPU Units product family page for the catalog overview.

The NS5-SQ11B-V2 is a 5.7-inch QVGA STN NS-series Programmable Terminal with a 10/100Base-TX Ethernet port. It supports FINS/UDP, FINS/TCP, and EtherNet/IP for PLC communication. See the NS-series PT product family page for the catalog overview.

Both ports auto-negotiate speed/duplex, but for commissioning it is best to lock both sides to 100 Mbps / Full Duplex unless the switch infrastructure forces otherwise. Direct connection — no switch, no router — is a /30- or /24-style link, so traffic stays entirely on the two devices.

Cable Selection: Crossover vs Straight-Through

The single most overlooked item on a direct HMI-to-PLC link is the patch cable. Modern industrial Ethernet ports implement Auto-MDIX and will internally swap the TX/RX pairs, so in theory a straight-through cable works. In practice, firmware revisions and silicon revisions across the NS5 and CJ2M families have had intermittent Auto-MDIX issues when connected back-to-back. The robust field practice is:

1. First attempt: straight-through (T568B-T568B) patch cable. Both ports are full MDI/MDIX-capable, so a normal patch cord should link up.
2. If the LINK LED does not illuminate within ~5 seconds, swap to a crossover (T568A-T568B) cable. This eliminates any auto-negotiation or MDI/MDIX fault on either silicon revision.
3. Avoid cables longer than 50 m for bench work. Use a factory-terminated Cat5e or Cat6 patch cord < 3 m to rule out attenuation and pair crosstalk.

Verify the cable with a simple cable continuity tester (e.g., a Fluke MicroScanner or a generic RJ45 tester). All eight conductors must show end-to-end continuity, and pairs 1-2 and 3-6 must not be reversed. A reversed pair is the most common failure mode of a hand-crimped crossover cable.

IP Address Configuration and Subnet Verification

The reported IP plan is:

Confirm on the bench:

1. Both addresses are in the same /24 network (192.168.250.0/24). The third octet (250) must match; the host portion (198 vs 199) must be different.
2. Neither address is the network address (.0) or the directed broadcast (.255) of the subnet.
3. The subnet mask on both devices is 255.255.255.0. A common mistake is leaving the HMI at 255.255.0.0 from a previous project — it will still ping locally but route FINS/UDP packets incorrectly.
4. No static gateway is set on either device. With a /24 direct link, the gateway field must be 0.0.0.0 on both sides. A stray gateway of 192.168.250.1 (an old default) will make the HMI ARP for a non-existent router the moment it tries to reach the FINS port.

CJ2M-CPU33 Built-in Ethernet Port Setup

The CJ2M-CPU33 front panel has a rotary IP address switch set (x16 and x1) located to the right of the Ethernet jack. This is what the operator is referring to as "the switches on the PLC." Their behavior is critical:

For a host octet of 198, the rotary pair should read x16 = 12 (hex C, decimal 12) and x1 = 6. Confirm by reading the etched legend on the CPU face plate — the value 198 = 12 × 16 + 6.

If the switches are at 0/0, the CPU is reading its IP from the project setting in CX-Programmer → PLC → Built-in Ethernet Port Settings → TCP/IP. Make sure that setting also reads 192.168.250.198 / 255.255.255.0; otherwise, switch and project disagree and the port will pick whichever it sees at power-up.

Also confirm that the Auto-MDI/MDIX and Auto-Negotiation settings in CX-Programmer match the actual HMI port. Locking the PLC to 100M / Full Duplex while the HMI is forced to 10M / Half Duplex will produce a partial link (LINK LED on, but no FINS traffic).

NS5-SQ11B-V2 Communication Configuration

The NS5 must have at least one Host defined in the CX-Designer project, and that Host's parameters must match the CJ2M port exactly. Open the project in CX-Designer and select PT → Host Types (or PT → Communication Settings, depending on CX-Designer revision):

The Host Type must be present and enabled. If the CX-Designer project has no Host defined at all, the NS5 will never initiate a session — the PT Status → Communications screen will read "No Host" even when the LINK LED is green and the ping works.

Protocol Selection: FINS vs EtherNet/IP

Omron HMIs and PLCs support two primary Ethernet protocols for PT-to-PLC traffic:

• FINS/UDP — Omron's native industrial protocol. Lightweight, multicast-capable, ideal for periodic data collection. Requires a routing table when crossing network boundaries; for a single direct link with no router, the routing table is still required but the entries are trivial.
• FINS/TCP — Connection-oriented variant. HMI opens a TCP socket to port 9600. No routing table needed because TCP handles session state, but slightly higher overhead.
• EtherNet/IP — Standard CIP over Ethernet. Used when integrating Omron with Rockwell or third-party CIP scanners. No FINS routing table needed. Recommended if the HMI is going to be one of several devices polling the same PLC.

FINS Routing Table Configuration

For any FINS-over-UDP traffic, the CJ2M must know the topology of the network it sits on. In CX-Programmer:

1. Open the project and go to PLC → Built-in Ethernet Port Settings → FINS Settings (or Tools → Routing Table on older CX-Programmer).
2. In the Local Network Table, define the network that the built-in port is on: Network #1, Node #198 — i.e., the IP's host octet.
3. In the Relay Network Table, declare how to reach the HMI's network. For a direct link, this is usually the same network, so the relay is the PLC's own port: Network #1 → Network #1 via Node #198.
4. Download the routing table to the PLC. After the download, cycle power or restart the Ethernet port. The PLC will not start FINS/UDP until this table is loaded.

Without the routing table, the PLC's FINS stack silently discards inbound FINS frames. The HMI reports timeout and the operator has no clue that the routing table is the cause.

Physical Layer Verification (LEDs and Cable)

The single LED on the CJ2M-CPU33 Ethernet jack area is split into two indicators (LINK/ACT and 100M). Confirm:

If LINK is OFF, do not waste time on CX-Designer. Swap the cable, try a different patch cord, then verify the HMI's port from its System Menu (System → Communications → Ethernet → Status). The NS5 should show "Link Up" on its own display before you touch any software setting.

Network Layer Verification (Ping and ARP)

Once the LINK LED is solid green on both ends, the cheapest test is a ping from a bench laptop connected to the same /24 subnet through a small switch:

ping 192.168.250.198
ping 192.168.250.199

Both must respond with < 1 ms latency. Then check the ARP cache:

You should see the MAC addresses of both Omron devices listed against their respective IPs. If the HMI does not appear in the ARP table after a ping, the NS5 is not actually on the subnet — re-check the subnet mask on the NS5's System Menu (a common cause is a leftover 255.255.0.0 mask).

Application Layer Verification (CX-Programmer and CX-Designer)

Step 1 — Verify PLC end-to-end with CX-Programmer:

1. Open the CJ2M project in CX-Programmer.
2. PLC → Connect Online, choose Ethernet (Built-in), target 192.168.250.198, port 9600 (FINS) or 44818 (EtherNet/IP).
3. If online connection succeeds, the PLC's IP, FINS, and routing table are all healthy. Move to step 2.
4. If online connection fails with a FINS routing error, the routing table download was not retained — re-download and cycle power.

Step 2 — Verify HMI project transfer with CX-Designer:

1. In CX-Designer, PT → Transfer → To PT.
2. Select Ethernet, target 192.168.250.199, model NS5-SQ11B-V2.
3. If transfer succeeds, the HMI's IP, subnet, and the host file are all valid; the only remaining variable is the host's protocol/port match.

Step 3 — Verify runtime communication from the HMI:

1. On the NS5, enter the System Menu (top-right corner of the screen during runtime).
2. Go to Comm. Status. The host row should show "Communicating" with green status.
3. Place a numeric display bound to D0 in the CJ2M, change D0 from CX-Programmer, and verify the value updates on the HMI within one scan.

Diagnostic Matrix: Symptom-to-Cause Mapping

Commissioning Checklist

1. Patch cable: verified straight-through first, crossover as fallback; both tested with a continuity tester.
2. Rotary switches: x16 = C (12), x1 = 6 for host octet 198, or switches at 0/0 with project IP set in CX-Programmer.
3. CX-Programmer online connect to 192.168.250.198 succeeds.
4. CX-Designer project contains a Host entry with the correct IP, FINS/EIP node, and port number.
5. CX-Designer transfer to NS5 at 192.168.250.199 succeeds.
6. Routing table downloaded to CJ2M and retained across power cycle.
7. HMI System Menu → Comm. Status shows "Communicating" on the host row.
8. Live bit / word changes from CX-Programmer are reflected on the HMI within one scan cycle.

Reference materials for further reading: the CJ2M CPU Units product family, the NS-series PT product family, and standard Windows Ethernet troubleshooting for the bench PC side. For general Ethernet diagnostics on a Windows host, the Microsoft Ethernet fix guide and the Dell wired networking KB are useful when the bench PC is the variable in the equation.