Tag Registration

A [tag] is a name given to one memory cell in a PLC. Since each PLC uses a different memory address notation, refer to the page for your specific PLC model.

• Mitsubishi: formats like D100, M50
• Siemens: formats like %DB1.DBW0
• LS: formats like D00309
• OPC-UA: formats like ns=2;s=Channel1.Device1.Tag1

For detailed notation, see the [PLC Address] section on each PLC page → PLC Type Guide

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Input Fields

Enter the following information for each tag line:

Field	What to enter
Tag Name	Name displayed on screen. Korean characters allowed (e.g., 펌프1 회전수)
PLC Address	Address notation from the PLC manual (e.g., D100)
Data Type	One of Float, Integer, Boolean, String, Long, Double
Format Helper (format)	DW for 32-bit, REAL for floating-point, etc. (optional)
Formula	Post-processing expression such as unit conversion (optional). See Apply Formula for details
Description	Notes. Displayed alongside the tag on screen

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Data Type Guide

Data Type	Width/Sign	When to use	Example
Boolean	1 bit	On/off, ON/OFF	Pump running / Alarm ON
Integer	16-bit signed	Integer (including negatives) — most common	Counter, rotation speed
Long	64-bit signed	Large integers (exceeding 32-bit)	Cumulative production count
Float	32-bit float	Values with decimal points	Temperature, pressure, speed
Double	64-bit float	High-precision decimal values	Precision measurement data
String	Variable	String	Batch name, recipe name

Precision types that specify sign/width in the name (same meaning as Kepware):

Data Type	Width/Sign	When to use
Short	16-bit signed	Same as Integer (explicit name)
Word	16-bit unsigned	0–65535 counter (no negatives)
DInt	32-bit signed	32-bit integer (replaces old Integer+DW combination)
DWord	32-bit unsigned	Cumulative counters exceeding 2.1 billion (2^31) — values that used to fail with Integer
QWord	64-bit unsigned	Large unsigned counters
Byte	8-bit unsigned	Status byte

Existing Tag Migration (behavior change effective 2026.07)

• S7 Integer: Corrected from misreading as unsigned (u16) to signed (s16) — resolves the issue where negatives appeared as values like 65531. Use Word if unsigned is needed.
• S7 / MELSEC Long: Unified from 32-bit reading to 64-bit standard. Tags previously reading 32-bit via Long should be changed to DInt (signed) or DWord (unsigned).

Array Tags (Base[N])

Registering in the format elementType[count] as in DInt[10] reads a contiguous region as a single tag and stores it as a JSON array string ("[1,2,3]"). Supported drivers (expanded as of 2026.07): EIP + MELSEC / S7 / Modbus / LS. Only numeric element types are actually collected. (String arrays cannot be registered; Boolean/Byte arrays are unsupported by drivers — values will be empty.) Per-driver limits: Modbus total 125 words · LS total 64 words · MELSEC by series (Q/L·iQ-R 960 / QnA 480 / A 32 words) S7 negotiated PDU − 19 bytes — if exceeded, values are empty, so reduce N or split the tag. Array tags are read-only (write not supported).

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Format Helper (format) Guide

Even with the same PLC address, the value can differ depending on how it's interpreted. This includes cases like combining two 16-bit memory cells to read as 32-bit, or combining four cells to read as a 64-bit float.

Your value type	데이터 형식	형식 보조
16-bit integer (most common)	Integer	(leave empty)
16-bit unsigned integer	Integer	UI
32-bit integer (two memory cells)	Integer	DW
32-bit float (most common float type)	Float	REAL
64-bit float (high precision)	Double	LREAL
1 bit (on/off)	Boolean	(leave empty)
Specific bit within a word	Boolean	BIN[3] (bit 3)
String of N characters	String	STR[N] (e.g., STR[10])

When values look wrong

If you have a 32-bit / 64-bit value but leave the format helper empty, it will be misread as 16-bit, making the value abnormally small or large. In that case, fill the format field with values like DW, REAL, LREAL.

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Advanced Tag Settings (Kepware Reference)

Tags can also store the following optional settings (if all unset, existing behavior remains). Currently specified via backup/restore JSON (/connect/restore) or REST; values are stored alongside the tag row.

Setting	Value	Meaning
byte_order	AB_CD BA_DC CD_AB DC_BA	32/64-bit byte/word order (unset = protocol default)
scaling_type	linear sqrt	Raw value → engineering unit conversion
raw_low/raw_high	number	Scaling input (raw) range
scaled_low/scaled_high	number	Scaling output (engineering) range
clamp	true/false	Clamp output to scaled range
negate	true/false	Sign inversion
units	string	Unit label (e.g., degC)
client_access	R / RW	When R, write API is rejected (read-only)
deadband	number	Skip publishing if change from previous value is below this threshold
scan_divisor	integer	Read once every n cycles (multiple of collection interval)

Example — linear conversion of raw 0..4095 from 4–20mA to 0..100%, with minor fluctuation suppression:

{"tags":[{ "opc_id":"OPC_X", "tag_id":"TAG_PCT", "tag_name":"압력%",
  "data_type":"Float", "plc_address":"D100",
  "scaling_type":"linear", "raw_low":0, "raw_high":4095,
  "scaled_low":0, "scaled_high":100, "clamp":true, "deadband":0.5 }]}

Can be used together with formulas (fomula) — the formula is applied on top of the scaling result.

The same settings can be specified in CSV batch registration (/ui/connect/csv) — optional columns after the default 9 columns: RAW_TYPE, BYTE_ORDER, SCALING_TYPE, RAW_LOW, RAW_HIGH, SCALED_LOW, SCALED_HIGH, CLAMP, NEGATE, UNITS, CLIENT_ACCESS, DEADBAND, SCAN_DIVISOR, TAG_GROUP. Existing 9-column CSVs work unchanged. JSON backup/restore always includes these settings (items unset are omitted from the file).

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How to Register

Method 1 — Add Together in the PLC Registration Form

The [Add Connection] or [Edit] screen includes a tag input table. Press the [+ Add Tag] button to add a row, enter each tag line by line, then press [Save].

Method 2 — Add Tags to an Already Registered PLC

1. [Connections] menu → click the PLC on the left
2. Click the [Add Tag] button above the [Tag List] on the right
3. Add tags one by one. Values start coming in at the next collection interval immediately.

Method 3 — CSV Batch Upload

If you have dozens or more tags, the [CSV Batch Upload] button at the top right of [Connections] is faster. The CSV template can be downloaded from the upload screen.

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Verifying Registration

Click on the PLC to see registered tags in the [Tag List] on the right.

Column	Meaning
Tag Name / Address / Type	As registered
Current Value	Most recently collected value (auto-refreshes every 5 seconds)
Collection Time	When that value was received
Status	정상 / 오류

If an error appears, it's likely a typo in the PLC address notation or a data type mismatch. Refer to Troubleshooting — Values look wrong.

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Modifying / Deleting Tags

• Click a row in the tag list to open the edit form.
• Use the [Delete] button at the end of each row to delete one at a time.

Changes apply at the next collection interval.

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FAQ

Q. How do I find out the PLC address?

• PLC programmer / equipment manufacturer manuals often include a "data mapping table."
• You can check addresses in use via the "Watch table / monitor screen" in PLC programming tools (GX Works, TIA Portal, XG5000, etc.).
• For OPC-UA, using a free client like UA Expert to click/copy addresses is the most accurate method.

Q. How is the tag ID assigned?

The gateway automatically assigns IDs in the <connection-id>_TAG_<number> format. You can specify them manually, but only use English letters, numbers, and underscores.

Q. Can I register the same address as two tags?

Yes. This is often used when applying different formulas to the same raw value to send it in two units (e.g., temperature raw + temperature_F Fahrenheit conversion).

Q. How many tags can I register per PLC?

Several hundred is no problem. However, since all must be read within the collection interval, consider how much time the PLC needs to respond. If tags for one PLC exceed 1000, it's advisable to monitor PLC load / network latency as well.