Industrial Engineer · phase 5 of 16

RPI

Requested Packet Interval, the configured rate at which a CIP I/O connection requests data updates.

The Explain card

Plain English: The requested packet interval is how often a controller asks a device to exchange implicit data. It is set per connection, in milliseconds.
Example: A safety I/O block is set to a 10 millisecond RPI, a temperature module to 250 milliseconds. The controller schedules both and the network carries them at those rates.
Why it matters: Faster RPIs mean fresher data and more traffic, and a rack full of devices at 2 milliseconds saturates a controller's connection budget. The default is rarely right for everything, so set each RPI to what the process actually needs.
Hook: How often you want to hear from it.

How the word is built, where it came from, and what it sits beside in memory.

In a sentence

During EtherNet/IP commissioning, set the remote I/O adapter's RPI to 20 ms, then confirm the connection remains stable under normal network load.

Letter by letter

Where it came from

Origin: English industrial-networking coinage formed from the initials of Requested Packet Interval
Entered the language: 1990s
What changed: It began in ControlNet and CIP connection terminology and later carried into EtherNet/IP device configuration.

How it is spelled

Capitalisation: Always written RPI in capitals, including mid-sentence
Plural and possessive: Plural RPIs; singular possessive RPI's; plural possessive RPIs'
Out loud: Spelled out letter by letter.

Same family

Broken into chunks

What it sits beside

Same subject

Same shape

CIP connection parameters

industrial-network initialisms

Phase 5: PLC Industrial Communications

The protocols that let controllers, drives and operator panels talk, plus the addressing and description files that make them agree on what was said.