← SCADA, Industrial Controls & Automation
🗃️

Modbus Register Explorer

Virtual slave · Coils · Discrete · Holding · Input registers · Live read/write

When to use: Use this to learn how a Modbus master talks to a slave device. The device exposes four data tables — Coils (R/W bits), Discrete Inputs (RO bits), Holding Registers (R/W 16-bit), and Input Registers (RO 16-bit). Choose a function code, address (0–15), and value, then Execute to read or write. Enable Live to watch input registers update like real field sensors. The transaction log shows each request just like a Modbus poll trace.

📡 Master Request

4xxxx
Read operation — no value

📜 Transaction Log

No transactions yet — execute a request.
Modbus Reference: Coils (0xxxx) and Holding Registers (4xxxx) are read/write; Discrete Inputs (1xxxx) and Input Registers (3xxxx) are read-only. Registers are 16-bit (0–65535). The PDU address here is 0-based; a master library may show 1-based reference numbers.

Coils (0xxxx · R/W)

0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15

Discrete Inputs (1xxxx · RO)

0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15

Holding Registers (4xxxx · R/W)

0
100
1
110
2
120
3
130
4
140
5
150
6
160
7
170
8
180
9
190
10
200
11
210
12
220
13
230
14
240
15
250

Input Registers (3xxxx · RO)

0
200
1
201
2
202
3
203
4
204
5
205
6
206
7
207
8
208
9
209
10
210
11
211
12
212
13
213
14
214
15
215