Logix reaches its I/O over EtherNet/IP, which is CIP running on Ethernet. Add a module to the I/O tree and Logix creates its tags for you automatically. Set the module's RPI and you have set how often it exchanges data. Add a remote rack below and watch its tags appear.
The tree starts with just the controller and its Ethernet port. Press ➕ Add module to drop in a remote 16-point input card, then watch its tags (Conv:1:I.Data …) appear under it automatically. There is no addressing and no mapping table, because the module's profile tells Logix exactly what tags to make. Slide the RPI to set how fast it updates.
The cyclic connection the RPI controls: module data ↔ controller tags, exchanged automatically every RPI. This is how your I/O updates.
On-demand reads/writes through the MSG instruction (last track), used for configuration and occasional data, with no connection held open between messages unless you tick Cache Connections.
A lower RPI means faster updates, but also more network traffic and more packets per second for the Ethernet module to handle (each module has a finite packet budget). The RPI does not change how many connections a module uses. Tune it to the signal: 2 ms for fast interlock I/O, 50–100 ms for a temperature you read lazily. The I/O tree is your hardware configuration, and it writes your I/O tags for you as a side effect.
📡 Implicit (I/O) messaging carries high-speed cyclic data on a standing connection, paced by the RPI. Your input/output modules and produced/consumed tags use it. Once it is configured, it runs on its own.
✉️ Explicit (MSG) messaging is request/response transactions you trigger with the MSG instruction. Use it to read a drive parameter, send a recipe, or talk to a device that is not in your I/O tree.
It is the same idea as last track's produced/consumed (implicit) vs MSG (explicit), applied here to physical I/O. EtherNet/IP carries both kinds on one wire, alongside your HMI and historian traffic.
A temperature input changes slowly and your Ethernet module is close to its packet-rate limit. What RPI is sensible?