Configuring Omron Serial FINS Communication Wiring and Protocol

Configuring Omron Serial FINS Communication: Wiring and Protocol Setup

Omron's FINS (Factory Interface Network Service) protocol operates on three physical layers: Ethernet (UDP/TCP), RS-232C, and RS-422A/485. Serial FINS remains the dominant choice on legacy CS/CJ-series racks and on CP-series compact PLCs because it preserves Host-Link framing at the byte level while layering the FINS service set on top. This reference covers wiring, framing, addressing, and driver configuration for any host that speaks serial FINS — CX-Programmer, SCADA, a custom .NET/AdvancedHMI client, or a C-more HMI panel.

FINS Protocol Architecture

A FINS message is a framed packet consisting of a Host-Link-compatible wrapper, a 16-byte FINS header, and a command-specific data block. Three addressing parameters must match between the host and the target PLC:

The full FINS header layout (16 bytes) is documented in the CS/CJ/CP/CJ2-series Communications Commands Reference Manual (W342). The four most significant header bytes are reserved for the ICF, RSV, GCT, and DNA fields; the next bytes specify destination network (DA1, DA2, SNA) and source identification.

Supported PLC Families and Ports

Serial FINS is implemented on the following Omron product families. Each uses a slightly different framing for the same byte-stream service:

RS-232C Wiring — Direct Cable Pinout

The classic Omron serial cable (Omron p/n XW2Z-200S for 2 m, XW2Z-500S for 5 m) implements a null-modem-style crossover suitable for the CS/CJ/CJ2 DB-9 port. PC COM port pins on the left, PLC DB-9 pins on the right:

This is a 3-wire active crossover: pins 2↔2 and 3↔3 cross to swap TX/RX, while pins 7↔4 and 8↔5 give hardware handshaking using the PLC's DTR/DSR signals. Pin 5↔9 establishes common ground. Do not cross pins 2↔3 and 3↔2 in the wrong direction — the PLC simply will not respond and no LED activity will appear on either side.

Serial Frame Parameters

All four parameters must match on PC and PLC. Default Omron values are shown in bold:

The PLC's CPU serial port is configured through the PLC Setup area in CX-Programmer. For CS/CJ the settings reside in DM areas DM32000 (port 1) and DM32010 (port 2) when Peripheral Bus mode is disabled. Set the relevant word to the four-digit hex value where lower nibble = baud rate code, next nibble = data/para/stop bit pattern, and upper byte = node number.

Step-by-Step: Configuring Serial FINS with CX-Programmer

The fastest path to a working communication link is to let CX-Programmer auto-discover the parameters. Once the link is up, copy those values into your host application.

Prerequisites

• CX-Programmer (CX-One or Sysmac Studio) installed on the host PC.
• Approved serial cable (XW2Z-200S for 2 m, XW2Z-500S for 5 m, or CP1W-CIF01 for CP-series).
• PLC and PC powered, with PLC in PROGRAM or MONITOR mode (communication works in RUN too, but be cautious).
• USB-to-RS232 adapter verified working at full-duplex (e.g., FTDI FT232 chipset recommended; avoid cheap CH340 converters for field commissioning).

Procedure

1. Open CX-Programmer and create a new project for the correct CPU family (CS1G, CJ2M, CP1L, etc.). When prompted for the device type, choose the actual CPU — auto-online works for all families but the offline program upload will only match the project type.
2. Click Auto-Online (PLC → Auto Online → Auto Online with Windows Dialog…). CX-Programmer scans the COM ports, transmits probing Host-Link frames, and reports the COM port, baud rate, data bits, parity, and stop bits it found. Write these down — they are the canonical settings for your PLC's serial port.
3. Verify the discovered parameters with a manual Transfer to PLC of a small known change (e.g., toggle a contact) to confirm full bi-directional communication. If the Transfer succeeds, the link is solid.
4. Quit CX-Programmer completely. The Omron serial driver reserves the COM port for its exclusive lifetime; any other process holding the port — including a stuck background sync task — will prevent the SCADA or HMI driver from opening it.
5. Configure your host driver (AdvancedHMI, Ignition, TOP Server, C-more, Node-RED, etc.) with the exact COM port, baud, data, parity, and stop values recorded earlier. Enter the FINS routing triplet: Target Network, Node, and Unit.
6. Set network/node/unit on the driver side:
   • Network destination (= 0 in a single-PLC cell, = 1 if bridging through a serial->Ethernet gateway).
   • Target Node = PLC's node address set on its rotary switch (commonly 01).
   • Unit = 0 for the CPU's built-in port, 1 for slot 1 option board, etc.
7. Do not configure the PLC to transmit data unsolicited at this stage. The host driver polls the PLC on a cycle and unsolicited writes from the PLC side can corrupt the receive buffer of the driver, which typically presents as intermittent "tag quality bad" events. Use the PLC's scheduled SEND(090) only if the SCADA supports a periodic-write model.
8. Test by reading a known word (e.g., D100 in a free data-memory area). If the response times out and the SD/RD LEDs on the PLC show no activity, revisit wiring and parity; if SD flashes once per second but no RD response follows, the host-to-PLC frame is correct but node numbers do not match.

Configuring a C-more Panel (HMI Side)

When the host is an AutomationDirect C-more HMI, the FINS implementation is treated as an Omron CPU serial protocol. The C-more help topic 247 documents the panel-side setup:

1. On the panel project, right-click Protocol Setup and add an Omron CPU Serial protocol.
2. Enter the PLC Node Address (0–31; default 0).
3. Set the port parameters: baud, data bits, parity, stop bits. These must match the PLC exactly.
4. Set the Scan Rate — the interval the panel waits between executing a complete read sequence of the displayed screen (typically 500 ms for status panels, 200 ms for control panels).
5. Map each tag to an Omron memory area (CIO, DM/HR/WR/EM-bank) using FINS byte/word addresses.

Driver Map Across Host Platforms

Verifying the Link

The strongest possible proof of a working FINS link is a successful MRC 0x01 0x01 (Memory Area Read) against a known address. Confirmation steps:

1. Read a status word — for a CS1G use DM00100, or anywhere in CIO 000–CIO 6143.
2. Read the PLC model/identifier with MRC 0x05 0x01 to confirm node routing.
3. Read CPU Unit Status with MRC 0x06 0x01 for a heartbeat
4. Watch SD and RD LEDs on the PLC — both should toggle consistently with the poll interval.

If the PLC ERR/ALM LED is lit, capture the CPU error from CX-Programmer (Diagnostics → PLC Errors) before continuing; many communication problems are downstream symptoms of CPU faults such as cycle-overrun or I/O bus errors.

Troubleshooting Matrix

FINS Error Codes and Recovery

The end codes returned in the FINS response frame byte 18 (ERR) carry diagnostic value. The most common serial-FINS errors and their interpretation per W342:

Intermittent Drop-Out Field Pattern

A pattern frequently reported with serial-FINS drivers — including the Inductive Automation FINS thread — is intermittent loss of tag quality that persists until the host driver is restarted. The underlying problem is almost always:

1. The connection is reported as bound at the device level even while no traffic flows.
2. A single corrupted frame leaves the driver's receive-state machine out of sync.
3. The polling task continues to write to a buffer expecting a FINS response that never matches.

Mitigation in driver configuration:

• Enable the watchdog / heartbeat option if available.
• Set FINS session timeout to a value slightly longer than the longest expected PLC scan (default often 3 s).
• Verify that nothing else is using the same physical COM port — including the Omron FINS Gateway service which can sit transparently between CX-Programmer and the driver.
• Replace USB-RS232 adapter when the field test confirms intermittent fails with bad-CRC bytes; the controller side is rarely at fault.

Ethernet FINS as a Successor

Most engineers moving off serial FINS move to Ethernet FINS for the higher poll rates (up to 4,096 words per message, 100/10 Mb/s wire speed) and easier cable management. The driver configuration is identical — same header, same MRC/SRC codes, same network/node/unit addressing — only the Connection Mode property changes from Serial to UDP or TCP on the TOP Server Ethernet FINS driver. node-red-contrib-omron-fins supports CV, CP, CS, CJ, NJ, and NX across both transports with the same API.

Final Commissioning Checklist

1. CX-Programmer auto-online completes and reports a known node at the target COM port.
2. A successful two-way transfer (PC-to-PLC upload and PLC-to-PC verify) confirms hardware.
3. Host driver is configured with the recorded baud/frame/node/network/unit triplet.
4. Host reads a known boolean (CIO 100.00) and a known word (D100) within one poll interval.
5. PLC SD and RD LEDs both flash in rhythm with the host poll.
6. CPU is in RUN or MONITOR mode without ERR/ALM lights.
7. Host driver logs show no overrun or NACK for at least 5 minutes of continuous polling.
8. Watchdog / auto-reconnect enabled in the host driver to recover from any future field-induced cable noise.

Frequently Asked Questions