The Modicon M580 platform is designed to provide deterministic and predictable recovery performance on its Ethernet Remote IO network. One of its key strengths is the ability to maintain a 50 millisecond recovery time when using validated Remote IO devices such as the BMECRA, Modicon Edge IO NTS, and certain Altivar drives. This level of performance is possible only when the system architecture is fully validated and all components follow the required configuration and communication standards.
The M580 also supports recovery through the Rapid Spanning Tree Protocol (RSTP) on the Ethernet Device Network ports located on the front of the controller (ETH2 and ETH3). RSTP is an IEEE 802.1D protocol that helps maintain a loop‑free logical network and automatically restores communication when a link is lost.
RSTP provides the following functions:
- It creates a loop‑free Ethernet topology when redundant physical paths exist.
- When either Device Network port is disconnected, RSTP automatically forwards traffic through the alternate port.
- It restores communication by activating redundant links during a network event.
During an RSTP reconnection, the protocol may take up to 50 milliseconds to re‑establish the correct forwarding path, and some packets may be lost during this transition. All network switches must support RSTP for this feature to work correctly.
The service port, which is the uppermost of the three Ethernet ports on the front of the CPU (ETH1), does not support RSTP and should not be connected to the Device Network, either directly or through a switch or hub. Doing so can create logical loops and negatively impact network performance. The service port also does not support VLANs or QoS tagging, which makes it inherently non‑deterministic.
It is important to note that the guaranteed 50 ms recovery time applies only to validated eRIO devices. When using distributed devices that are not validated for Schneider Electric’s Remote IO architecture, the system cannot meet the same recovery time requirements. Third‑party IO devices have unpredictable behavior and features that cannot be guaranteed within the deterministic M580 environment. In addition:
- Distributed IO (DIO) data is not transmitted in real time and is queued behind eRIO data.
- DIO traffic uses only the remaining bandwidth after eRIO packets have been delivered, making its timing inherently non‑deterministic.
If the you would like to include distributed equipment to participate on the eRIO network, then a DRS Modicon Switch must be used, and the architecture must follow one of the validated topologies described in the Modicon M580 Complex Topologies System Guide. Keep in mind that the 50 millisecond recovery time applies only to validated Remote IO devices on the eRIO network. Using a DRS Modicon Switch ensures proper participation on the eRIO network, but it does not make Distributed IO deterministic. DIO devices will still operate with non‑deterministic timing, since their traffic is queued behind RIO data and uses only the remaining bandwidth.
For more information on the M580 please reference:
- Modicon M580 Hardware Reference Manual
- Modicon M580 - Open Ethernet Network, System Planning Guide | Schneider Electric
