This glossary defines the industrial-automation terms used by the Binions Modbus integration. If you are wiring a programmable logic controller or a SCADA system into your playbooks, these are the words you will meet on the Modbus daemon and Industrial & Modbus pages. Each term is defined in one plain sentence.
Good to know. Modbus is a register-and-bit protocol: most of what you read or write is either a single on/off bit or a 16-bit number at a numbered address on the device.
| MODBUS | A long-established industrial protocol for talking to controllers and I/O devices. |
| PLC | Programmable logic controller — the industrial device Binions reads from and writes to. |
| SCADA | Supervisory control and data acquisition — the industrial systems that speak MODBUS. |
| MODBUS TCP/IP | MODBUS carried over a TCP network (the default transport). |
| RTU-over-TCP | MODBUS RTU framing tunnelled over TCP, for example through a serial-to-Ethernet gateway. |
| Coil | A single read/write bit (a digital output). |
| Discrete input | A single read-only bit (a digital input). |
| Holding register | A 16-bit read/write value. |
| Input register | A 16-bit read-only value. |
| Function code (FC) | The numeric code that names a MODBUS operation (read coils, write a register, and so on). |
| Register address | The numeric location of a coil or register on the device. |
| Device identification | Reading a device’s vendor, product, and version. |
| File record | A block of data some devices expose, read or written with extended function codes. |
| FIFO queue | A first-in-first-out buffer some devices expose for reading. |
| Server mode | Binions presenting registers to a SCADA master (read-only, opt-in). |
| Circuit breaker | A safety mechanism that stops hammering an unreachable device and retries later. |
| Rate limiter | A cap on how fast writes are sent to a device. |