Configuring Omron NS8 Ethernet Communication with CS1 ETN21/ETN11

1. Problem Overview

An Omron NS8-V2 series Programmable Terminal (PT) connected to a CS1-series PLC through a CS1W-ETN21 or CS1W-ETN11 Ethernet module displays "Connecting..." indefinitely and never establishes data exchange, even when the IP-layer ping succeeds and the on-board Comm Test screen returns valid responses to FINS command 0501 (Memory Area Read) addressed to N.n.u = 1.1.0. The project screens compile and download, but every numeric display and indicator reports ???? or *** because the runtime cannot bind symbolic tag addresses to a registered host.

This is one of the most common deployment faults on legacy NS-series installations: the IP parameters are correct, the cabling and switch port are healthy, and the FINS stack on the ETN module is responding to diagnostic queries, yet the NS-Designer project was never configured to publish the PLC as an Ethernet host. Without an explicit Host registration entry, the address library in NS-Designer will not offer the ETN: address prefix, and the runtime cannot construct the FINS frame from the PT side.

The fix is a two-part configuration change performed entirely inside NS-Designer (CX-Designer legacy): register the CS1/CJ1 PLC as a network host with an Ethernet transport, and disable any unused serial channels so the runtime does not poll them in parallel.

2. Affected Hardware and Firmware

The following combinations exhibit the symptoms described above. Confirm your units before applying the procedure.

3. Root Cause Analysis

Three independent misconfigurations commonly co-exist on a non-communicating NS8 link. They must all be resolved for the PT to bind tags.

3.1 PLC Host Not Registered in the NS Project

The NS-Designer project file (.IPS or compiled .IOM) carries a list of "Hosts" (external devices) that the PT may communicate with. When a tag such as D100 is placed on a screen, NS-Designer resolves the address against this host list to choose the wire-level transport and the address-prefix literal that will appear in the tag (e.g., CS1W-CN_00:D100, PT_CPU00:D100, or ETN_001:D100). If no Ethernet host is declared, only the serial-prefix options are visible in the address picker, which is exactly the symptom reported: "I cannot select the memory addresses to be ETN:####, only PT or SerialA."

3.2 Unused Serial Channels Left Enabled

The NS8 V2 has three logical ports: Ethernet, Serial A (RS-232C), and Serial B (RS-422A/485). Each enabled port occupies a FINS routing slot. If Serial A is enabled but no Host Link device is attached, the runtime continuously retries and the system flag for "comm error on serial" raises, masking the Ethernet health bit and flooding the system alarm log. This also causes the PT to display "Connecting..." on the bottom-right status indicator because at least one configured host is in error.

3.3 FINS-to-IP Conversion Not Performed

The NS8 speaks FINS over UDP/IP to the ETN21. The PT must be told how to map a FINS Network.Node.Unit triple to an IP address. On the ETN21, this is done by the FINS/UDP Routing Table in CX-Integrator (or written into the CPU's DM area). On the NS8 side, the equivalent is the Address Conversion Table in NS-Designer's PT settings → Comm. Without that table, FINS frame 0501 01 01 00 D0 0001 000A (read 10 words from D0 on node 1.1.0) is sent but the NS does not know to translate node 1 to IP 192.168.1.1, so the frame is dropped.

4. Pre-Commissioning Checklist

Before opening NS-Designer, confirm the following are correct so that a clean state is restored before host registration.

1. NS8 V2 IP: 192.168.1.2, subnet 255.255.255.0, gateway not required for a flat segment.
2. ETN21 IP: 192.168.1.1, subnet 255.255.255.0. FINS node address on ETN21 rear rotary switches set to 01 (decimal 1).
3. Ethernet cable: straight-through Cat5e or better, both link LEDs lit on NS8 and on the switch/ETN21 port.
4. From a PC on the same segment, ping 192.168.1.2 and ping 192.168.1.1 both succeed with <1 ms typical.
5. Confirm ETN21 FINS node is not a duplicate of the CPU's FINS node. On a CS1, the CPU itself holds a FINS node (default 00 hex → decimal 0). The ETN21 must hold its own distinct node; for this article we use 01.
6. Save the existing NS project to .IPP source as a backup. File → Save As → NS8_project_source.IPP.

5. ETN21 / ETN11 Network Setup

Configure the ETN module through CX-Integrator or by writing the DM area directly with CX-Programmer. The procedure below uses CX-Integrator, which is the recommended workflow.

5.1 IP Address and FINS Node

1. Connect CX-Integrator to the PLC via USB or Ethernet and start an online connection.
2. Right-click the CS1W-ETN21 in the rack and select Edit Node / Unit Information.
3. Set Node Address = 01 hex (decimal 1). This must match the rotary switches on the rear of the unit, otherwise the change is overwritten at next power-up.
4. Set IP Address = 192.168.1.1, Subnet Mask = 255.255.255.0.
5. Set Network No. = 1 to match the NS8 side.
6. Click Transfer to PLC and cycle power to the rack when prompted.

5.2 FINS Routing Table

The routing table tells the ETN21 how to forward FINS frames that are not destined for itself. With only one network, the default routing is sufficient, but you must still Transfer [Local Network Table] and [Remote Network Table] to the module:

• Local Network Table: Network 1, Node 1, ETN21 IP 192.168.1.1.
• Remote Network Table: empty in this single-network design.

5.3 ETN11 Differences

If you are using the older CS1W-ETN11, the same DM-area configuration applies, but the port is 10Base-T only. Ensure the switch on the network is 10/100 auto-negotiating or hard-set the NS8 port to 10 Mbps half-duplex through the System Menu → Comm → Ethernet → Speed setting. The NS8 V2 auto-negotiates correctly with most managed switches, but unmanaged 100 Mbps hubs will drop 10Base-T link with the ETN11.

6. NS-Designer Host Registration (Critical Step)

This is the step most often missed. Without a registered Ethernet host, no ETN: prefix is offered in the address library and no tags bind to the PLC.

6.1 Open Project Settings

1. Launch NS-Designer v3.3x (or compatible) and open the project .IPP file.
2. From the menu, choose PT → PT Settings (or press F8). The PT Settings dialog appears.
3. Select the Comm. tab. Two sub-tabs are visible: Host and Address Conversion.

6.2 Register the PLC as an Ethernet Host

1. In the Host sub-tab, click Add.
2. Set the following:

3. Click OK. The host now appears in the host list with the prefix CS1_ETN.
4. Right-click the new host and select Set as Active if multiple hosts are declared.

6.3 Disable Serial A and Serial B

1. Still in PT → PT Settings → Comm., locate the Serial Port section.
2. Set Serial A = Not Used.
3. Set Serial B = Not Used.
4. Click Apply.

6.4 Build the Address Conversion Table

1. Select the Address Conversion sub-tab.
2. Add an entry: FINS Network.Node.Unit = 1.1.0, IP Address = 192.168.1.1.
3. If the NS8 itself needs to be reachable from the PLC side (for instance, when the ladder triggers a screen change), also add the reverse: 1.2.0 → 192.168.1.2.
4. Click Transfer to PT when uploading the project.

6.5 Rebuild the Tag Library

With the host registered, open any screen and double-click a Numeric Display. In the address picker, the prefix CS1_ETN is now listed. Selecting it reveals the standard CS1 memory areas (D, W, H, A, CIO, EM) with the correct numeric range for the CPU. Tags already placed on screens with the legacy PT_CPU00: prefix must be re-mapped manually using Find and Replace, or by deleting and re-creating the affected components.

7. Download, Verification, and Comm Test

1. Compile the project: File → Compile. Address errors are reported at this stage if a tag points to an area the active host does not expose (for example, an EM bank that is not present on the target CPU).
2. Connect NS-Designer to the NS8 over USB or Ethernet and click Transfer → Project. Confirm the transfer dialog reports Transfer Complete with no errors.
3. On the PT, enter the System Menu by pressing the top-left and top-right corners of the touch screen simultaneously for three seconds, or by tapping the menu button on a spare corner.
4. Navigate to Comm Test. The diagnostic screen lets you send arbitrary FINS commands. Send 05 01 01 00 D0 0001 000A (Memory Area Read, 10 words from D0). The destination triple is N.n.u = 1.1.0. A successful response contains 20 bytes of word data; an error returns FINS completion code 0201 (local node not in network) or 0205 (response timeout).
5. Exit the System Menu and run the project. The bottom-right status indicator should now read Connected (green) instead of Connecting....

8. Fault Code Reference

The following FINS completion codes are returned when a host fails to respond. Use this table as a triage matrix when the link is still down after applying the host registration fix.

9. Edge Cases and Field-Proven Caveats

• Multiple ETN modules on one PLC. Each ETN must carry a unique FINS node. If you assign both to node 1, the second module is invisible to FINS routing. Use CX-Integrator's Detect Network tool to confirm uniqueness.
• CJ-series migration. If the CPU is later upgraded from a CS1H to a CJ2M, the host type in NS-Designer must be changed from CS1 / CJ1 (Ethernet) to the CJ2 profile, otherwise the address library does not expose the CJ2 expansion areas (e.g., the second EM bank).
• FINS/TCP vs FINS/UDP. The NS8 default is FINS/UDP. FINS/TCP requires both sides configured explicitly; do not change the transport setting without re-uploading the routing tables on the ETN21, otherwise FINS frames over TCP will be silently dropped.
• Power-up ordering. Always power the NS8 before the PLC. If the PLC boots first and the NS8 misses the initial FINS/UDP broadcast, the "Connecting..." state may persist for up to the FINS retry timer (default 5 s). Cold-start the PT side to clear.
• Static IP vs DHCP. The NS8 V2 supports DHCP, but for an industrial segment always hard-set static IPs. A transient DHCP lease change is a frequent cause of phantom "Connecting..." states in plants where IT managed switches run a DHCP server.
• Firewall on engineering PC. Windows Defender Firewall blocks UDP/9600 by default. When running the Comm Test from a remote PC, add a rule for inbound/outbound UDP/9600.

10. Recommended Documentation and Reference Manuals

• NS-series NS8/NS10/NS12 Catalog (V096)
• CS1W-ETN21 Ethernet Module Operation Manual (W420)
• CS1W-ETN11 Ethernet Module Operation Manual (W067)
• NS-Designer Operation Manual (V083)
• CX-Integrator Operation Manual (W464)
• CS1 Series Operation Manual (W339)

11. Verification Matrix

12. Frequently Asked Questions