PLC Control Word Calculator
Build a 16-bit PLC control word by selecting the command bits that should be active. Generate the resulting decimal, hexadecimal and binary control-word values.
What Is a PLC Control Word?
A PLC control word is a binary word whose individual bits are used as commands, requests or control states. One 16-bit control word can carry up to sixteen independent Boolean command signals.
The functional meaning of each bit depends on the PLC program, drive, controller or equipment manufacturer. One device may use bit 0 for an enable command while another may assign that function to a completely different bit.
How to Calculate a PLC Control Word
Each active bit contributes its binary positional value to the final integer.
Bit 1 = 2
Bit 2 = 4
Bit 3 = 8
…
Bit 15 = 32768
The final control word is the sum of all selected bit masks.
PLC Control Word Example
Suppose bits 0, 1 and 3 need to be active.
Bit 1: 2^1 = 2
Bit 3: 2^3 = 8
Control word: 1 + 2 + 8 = 11
The complete 16-bit representation is:
Hex: 000B
Binary: 0000000000001011
PLC Control Bit Values
| Bit | Decimal Mask | Hex Mask |
|---|---|---|
| 0 | 1 | 0001 |
| 1 | 2 | 0002 |
| 2 | 4 | 0004 |
| 3 | 8 | 0008 |
| 4 | 16 | 0010 |
| 5 | 32 | 0020 |
| 6 | 64 | 0040 |
| 7 | 128 | 0080 |
| 8 | 256 | 0100 |
| 9 | 512 | 0200 |
| 10 | 1024 | 0400 |
| 11 | 2048 | 0800 |
| 12 | 4096 | 1000 |
| 13 | 8192 | 2000 |
| 14 | 16384 | 4000 |
| 15 | 32768 | 8000 |
Binary PLC Control Word
The calculator always displays the result as a complete sixteen-bit binary word.
Control word: 0000000000001011
A 1 means the corresponding command bit has been selected. A 0 means that bit remains clear.
Hexadecimal Control Words
Hexadecimal is frequently used for PLC and industrial control words because four binary bits correspond exactly to one hexadecimal digit.
Hex: 000B
A complete 16-bit control word can therefore be written using only four hexadecimal digits.
Control Word vs Status Word
Control words and status words are related but serve different purposes.
| Word | Typical Purpose |
|---|---|
| Control Word | Sends commands or requests |
| Status Word | Reports states or conditions |
A PLC may send a control word to a drive and then receive a separate status word describing the drive’s current condition.
Why PLC Control Words Are Used
Combining many Boolean commands into one word allows multiple control signals to be transferred or stored efficiently. This is common in PLC communication, industrial drives, motion controllers, field devices and machine-control systems.
A controller can set or clear individual bits according to the command structure defined by the receiving equipment.
Important PLC Control Word Notes
Bit positions range from 0 through 15.
Bit 0 has decimal mask 1.
Bit 15 has decimal mask 32768.
Selected bits are set to 1.
Unselected bits remain 0.
This calculator does not assume what any PLC command bit means.
Never send a generated control word to equipment without checking the actual manufacturer’s control-word documentation and required operating conditions.