Physical and Data Link Layers
Sercos III supports standard IEEE 802.3 & ISO/IEC 8802-3 100Base-TX or 100Base-FX (100 Mbit/s baseband) Full Duplex physical layer (PHY) entities. 802.3-compliant Media-Access Controller (MAC) sub-layers are used. Autonegotiation must be enabled on each PHY, but only 100Mbit full duplex is supported. Auto (MAU -Embedded) Crossover is specified between the two Physical Medium Attachment (PMA) units present with a duplex port. These two units are referred to as the Primary Channel and Secondary Channel in the sercos III specification. Dual interfaces are required (two duplex interfaces per device). Within the sercos III specification the dual interfaces are referred to as P1 and P2 (Ports 1 and 2).
Read more about this topic: SERCOS III, General Architecture
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