PLC Status Word Decoder
Decode a 16-bit PLC status word into individual bit states and named machine conditions. Enter the raw status value and define what each bit means to identify active PLC status flags.
What Is a PLC Status Word?
A PLC status word is a group of binary status flags stored inside one integer word. Each bit can represent a separate machine, drive, process or controller condition.
A 16-bit status word provides sixteen independent bit positions numbered from bit 0 through bit 15. Depending on the PLC application, those bits may represent states such as ready, running, faulted, warning, interlocked, remote mode or other equipment-specific conditions.
How to Decode a PLC Status Word
First convert the status word into its 16-bit binary representation. Each binary position can then be inspected individually.
Binary: 0000000000001101
Active bits: Bit 3 Bit 2 Bit 0
If those positions have been assigned names in the PLC or equipment documentation, the raw bits can be translated into readable status conditions.
PLC Status Word Example
Using these example definitions:
Bit 1 = Running
Bit 2 = Fault
Bit 3 = Warning
and a status word of 000D hexadecimal:
= 0000000000001101 binary
Bit 0 = 1 → Ready ON
Bit 1 = 0 → Running OFF
Bit 2 = 1 → Fault ON
Bit 3 = 1 → Warning ON
The active named statuses are therefore Ready, Fault and Warning.
Bit 0 Through Bit 15
Bit 0 is the least significant bit of the status word and bit 15 is the most significant bit.
| 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 |
Why PLC Status Bits Need Custom Labels
There is no universal definition stating that bit 0 must mean Ready or bit 2 must mean Fault. The meaning of each position is defined by the PLC application, equipment manufacturer or communication profile.
For this reason, this decoder lets you enter your own bit descriptions instead of incorrectly assuming that every PLC or industrial device uses the same status-word layout.
Hexadecimal PLC Status Words
Status words are often displayed in hexadecimal because one hex digit represents exactly four binary bits. A complete 16-bit word therefore fits into four hexadecimal digits.
Hex: A315
Hexadecimal makes status words shorter to read while preserving the complete bit pattern.
Using Status Words for PLC Diagnostics
Status words allow multiple Boolean conditions to travel or be stored inside one compact word. Engineers and technicians can inspect the individual bits to determine which machine or controller states are currently active.
This can be useful when troubleshooting PLC logic, industrial drives, motion equipment, process controllers, remote I/O, communication devices and machine status interfaces.
PLC Status Word vs Control Word
A status word normally reports conditions from a device or PLC-controlled process. A control word generally travels in the opposite direction and contains command bits used to request actions or operating modes.
Reports conditions
Control word: Controller → Device
Requests commands
For that reason, status decoding and control-word construction are separate operations.
Important PLC Status Word Notes
Bit positions range from 0 through 15.
Bit 0 is the least significant bit.
Bit 15 is the most significant bit.
A bit value of 1 means that bit is set or active.
A bit value of 0 means that bit is clear or inactive.
The meaning of each bit is device- and application-specific.
Always use the actual PLC program, drive manual or equipment documentation when assigning status labels.