Introduction
You can configure two M580 safety PACs to perform peer-to-peer safe communications over Ethernet. The configuration is based on Modbus TCP scanner communication, embedded in a black channel.
The safety peer-to-peer communication functional overview is as follows:

The communication is performed by two elementary function blocks from the M580 safety block library, that manage the safety loop at a SIL3 level. The protocol detects transmission errors – including omissions, insertions, disordered sequence, delays, inaccurate addressing, and masquerade bits – and manages retransmissions.
This safe peer-to-peer communication is possible only between:
two M580 safety PACs with both CPU firmware 3.10 or earlier,
two M580 safety PACs with both CPU firmware 3.20 or later.