Backing Up Omron NT620C Programs Using NT Support Tool

Backing Up Omron NT620C Programs Using NT Support Tool

Overview

The Omron NT620C is a 5.7-inch color STN-LCD touchscreen terminal from the NT-Series product family. Like its siblings in the NT-Series (NT30C, NT610C, NT612G, NT620C/S), it stores its screen configuration internally and is programmed externally using Omron's NT-Series Support Tool. When documentation for the unit is missing or has been lost, the only practical way to recover the project, or to create a baseline backup before any modification, is to upload the program from the terminal over its Host Link serial interface.

This procedure is non-destructive: a "receive" operation from the HMI pulls the existing project into the PC without altering what is stored in the NT620C. Only a "transmit" (download) operation writes back to the terminal. Understanding this distinction is the foundation of safe field practice when no source backup exists.

The communication link shown in the on-screen setup menu of the NT620C is reported as Host Link 9600BPS. That single line identifies the three things that must match on both ends of the cable:

1. Protocol family: Host Link (Omron's C-mode / SYSWAY-compatible master-slave serial protocol, not Modbus, not NT-Link, not EtherNet/IP)
2. Physical layer: RS-232C point-to-point (RS-422 is also supported on the NT620C but is a separate wiring scheme)
3. Baud rate: 9,600 bits per second (the standard Host Link default for the NT620C at its rear-port DIP setting)

Prerequisites

Before attempting the backup, gather the following:

Critical: The USB-to-serial adapter must support all five hardware handshake signals. Adapters marketed as "3-wire" or "charge-only" will fail Host Link transfers, often silently. Use an FTDI-based adapter or a native COM port.

Understanding Host Link on the NT620C

Host Link (also called SYSWAY in some legacy documentation) is Omron's command/response protocol for serial communication between a PC acting as the host and a controller or intelligent terminal acting as the slave. For the NT-Series HMIs, the host is the support tool software and the slave is the NT620C.

The link parameters that must be agreed on both sides are:

The unit number is set either in the on-screen setup menu of the NT620C or via the DIP switch bank on the rear of the unit. The default of 00 matches the factory-shipped configuration of virtually every NT620C in service. If a previous integrator changed it, the menu must be consulted before connecting.

Cable and Pinout Requirements

The NT620C has two serial ports on its rear face: a 9-pin port intended for Host Link to a PC (RS-232C), and a multi-pin port that can be configured for either RS-232C or RS-422. For a PC backup using Host Link at 9,600 bps, the 9-pin RS-232C port is the correct interface.

The cable must be a null-modem type with full hardware handshake. The field report explicitly flags that the required cable needs "full handshake." That means at minimum the following signals must be cross-connected, not just TX/RX/GND:

• SD (Send Data) ↔ RD (Receive Data)
• RD ↔ SD
• RS (Request to Send) ↔ CS (Clear to Send)
• CS ↔ RS
• ER (Enable Receive / DTR) ↆ DR (Data Set Ready) or CD (Carrier Detect) depending on cable side
• SG (Signal Ground)

Omron's catalog numbering for the standard NT620C programming cable is the XW2Z-S family (commonly XW2Z-200S for 2 m, XW2Z-500S for 5 m). The exact Omron catalog number for the unit-number-zero NT-Series Support Tool cable is documented in the NT-Series Support Software Operation Manual along with the official pin mapping. Always cross-check the actual wire-by-wire schematic in that manual before using a third-party cable, as incorrect DTR/DSR cross-over is the most common cause of intermittent Host Link timeouts.

Pinout ambiguity: The source material does not enumerate the exact DB-9 pin numbers for the NT620C port. The official pin map is only documented inside the manufacturer manual referenced above. Do not assume a generic PC-to-PC null-modem wiring will work; verify against the manual for the specific terminal revision.

DIP Switch and On-Screen Configuration

Two layers of configuration govern Host Link operation on the NT620C:

1. On-screen setup menu: Enter the NT620C system menu by pressing a designated corner of the touch area during power-up, or via the maintenance switch on the rear. Navigate to the communication settings screen and confirm Host Link is selected, baud rate is 9600, unit number is the value expected by the PC software, and the port is the RS-232C 9-pin connector.
2. Rear-panel DIP switches: The NT620C has a small DIP switch block that physically enables Host Link on the 9-pin port and selects the unit number's lower nibble. With the screen menu showing Host Link 9600 BPS, the matching DIP configuration is already in place; do not re-toggle without first recording the existing positions.

If the on-screen menu and DIP switches disagree, the DIP switches win for port selection and unit number, while the on-screen menu controls baud rate, data bits, parity, and stop bits. Always reconcile both before opening the support tool.

NT-Series Support Tool Software

Two generations of the support tool are in circulation:

The Windows version 4.7 was developed for Windows 3.1 and remains functional under XP. It is not a native Windows NT/2000/XP program in the modern sense; it expects the legacy Win16 runtime. On Vista and later, expect to run it inside an XP Mode virtual machine or a Windows 3.1 emulator such as DOSBox with a virtualized COM port, because later Windows releases removed the Win16-on-Win32 compatibility layer.

The current reference document is the NT-Series Support Software Operation Manual (V028), which is the canonical source for every screen-data creation, transfer, and verification procedure applicable to the NT30C, NT610C, NT620C, and the /S revisions.

Color Display Requirement

When creating new screen data for the NT30C, NT610C, or NT620C, the host PC running NT-Series Support Tool must have a color display. Monochrome-only displays cannot render the on-screen color palette correctly and the software will either refuse to load the project or will display mismatched colors that lead to mis-edits. The NT620C/S and NT612G models have their own additional notes documented in the manual; check the applicability table before assuming a 1:1 match.

For a receive-only backup, this color requirement is software-side only and does not affect the unit itself, but if the recovered project is to be opened on the same PC for verification, that PC must also be color-capable.

Pre-Transfer Safety Checks

Before issuing the receive command, confirm the following:

1. Receiving is safe. The NT-Series Support Tool's Receive operation only reads data from the NT620C; it does not write back. Only Transmit modifies the terminal's flash. This is the single most important field-engineering fact to internalize when working on a line with no backup.
2. Power is stable. A brown-out during receive aborts the transfer partway. The NT620C's on-board program is not corrupted by an aborted receive, but the resulting PC-side file may be incomplete and unusable.
3. Correct COM port selected. In the support tool, the COM port number must match the physical port the cable is plugged into. Using COM1 when the cable is on COM2 is the most common cause of "no response" errors.
4. Project name and number. Pre-decide the destination filename and the NT-Series project number. The default unit number on the NT620C is 00; the support tool's project number field must match.

Backup Procedure (Step-by-Step)

1. Power down the NT620C and connect the XW2Z-S (or verified equivalent) cable between the NT620C's 9-pin Host Link port and the PC's COM port. Tighten both connector screws.
2. Power on the NT620C and let it complete its self-test until the operator screen appears.
3. Enter the system menu on the NT620C and confirm Host Link, 9600 BPS, unit number 00 (or whatever the unit is set to), and that the 9-pin port is the active one.
4. Put the NT620C into transmit mode. From the system menu, navigate to the screen-data transfer menu and select Transmit (from HMI to PC). The terminal will display a "waiting for host" or "ready to send" prompt and will hold until the PC initiates the receive. The terminal does not push data on its own.
5. Launch the NT-Series Support Tool on the PC. From the project menu select the model as NT620C (or NT620C/S, matching the unit's actual revision).
6. Configure the PC-side communication in the support tool's transfer settings: COM port = the physical port number; Baud = 9600; Data bits = 7; Parity = Even; Stop bits = 2; Protocol = Host Link; Unit number = 00.
7. Initiate the receive in the support tool. Depending on the version, this is under File → Receive, Transfer → Receive, or PC → Receive from PT. The software will send a Host Link polling/select command to unit 00; the NT620C, already in transmit mode, will respond and begin uploading screen blocks.
8. Monitor the progress bar. A typical NT620C project transfers in tens of seconds to a few minutes depending on project size. If the progress bar stalls for more than 30 seconds, cancel and re-check cable/handshake.
9. Save the file to a directory that is backed up at the plant level. Save twice: once as the editable .nt6-class project file, once as a flat binary export if the support tool supports it.
10. Cycle power on the NT620C to return it to normal operator-screen mode. Transmit mode is not persistent across a power cycle.

Verification

After the receive completes, perform the following checks before treating the backup as valid:

1. Open the saved project in NT-Series Support Tool and confirm the project lists the correct number of screens.
2. Spot-check three screens: the initial/power-on screen, one operator screen, and one alarm or trend screen. Each must display with the expected labels, button text, and any bit/word references populated.
3. Cross-check tag references. Open the tag/address table inside the support tool and confirm the host (PLC) addresses referenced by the screens exist in the current PLC project. Mismatches here mean the screen was edited in the field and the PLC program drifted.
4. Note the project size in the support tool's project-info screen. Compare to the size reported when the original was first commissioned (if available) to detect truncated transfers.
5. Re-receive the same NT620C a second time and binary-compare the two files. They should be byte-identical. Any difference indicates non-deterministic transfer or a flaky cable.

Troubleshooting Matrix

Field-Proven Caveats

Three field-engineering lessons are worth recording before the first attempt on a production line:

• Receiving never alters the unit. Operators and managers who are unfamiliar with the tool will sometimes refuse to allow a backup for fear of corrupting the running screen. The protocol itself is read-only in the receive direction. This must be communicated clearly so that the backup can proceed before any other change is made.
• Disconnect the HMI from the running PLC before receive if the NT620C is the only Host Link device on the bus and shares a unit-number space with the PLC. Otherwise the PC may inadvertently address the PLC and either poll-storm it or write a register. When in doubt, pull the Host Link cable out of the PLC side during the backup window.
• Version-stamp every backup in the filename (NT620C_LINE3_2024-05-12_PRE-EDIT.nt6). Future comparisons depend on this.

Notes on Adjacent Models

The same receive procedure applies to the NT30C and NT610C, which share the Host Link 9,600 BPS configuration. The NT612G and the NT620C/S revisions carry specific settings that are documented in the NT-Series Support Software Operation Manual; do not assume the /S suffix is purely cosmetic, as it changes which screen-data blocks are valid for transfer. When in doubt, select the model that matches the exact suffix printed on the unit's nameplate, not the model printed on the original box or invoice.

FAQ