SLLSEC6E September 2012 – June 2019 DP83848-EP
PRODUCTION DATA.
The DP83848-EP supports both half and full duplex operation at both 10 Mbps and 100 Mbps speeds.
Half-duplex relies on the CSMA/CD protocol to handle collisions and network access. In Half-Duplex mode, CRS responds to both transmit and receive activity in order to maintain compliance with the IEEE 802.3 specification.
Because the DP83848-EP is designed to support simultaneous transmit and receive activity, it is capable of supporting full-duplex switched applications with a throughput of up to 200 Mbps per port when operating in 100BASE-TX. CSMA/CD protocol does not apply to full-duplex operation so DP83848-EP disables its own internal collision sensing and reporting functions and modifies the behavior of Carrier Sense (CRS) such that it indicates only receive activity. This allows a full-duplex capable MAC to operate properly.
All modes of operation (100BASE-TX and 10BASE-T) can run either half-duplex or full-duplex. Additionally, other than CRS and Collision reporting, all remaining MII signaling remains the same regardless of the selected duplex mode.
It is important to understand that while Auto-Negotiation with the use of Fast Link Pulse code words can interpret and configure to full-duplex operation, parallel detection can not recognize the difference between full and half-duplex from a fixed 10-Mbps or 100-Mbps link partner over twisted pair. As specified in the 802.3u specification, if a far-end link partner is configured to a forced full duplex 100BASE-TX ability, the parallel detection state machine in the partner would be unable to detect the full duplex capability of the far-end link partner. This link segment would negotiate to a half duplex 100BASE-TX configuration (same scenario for 10 Mbps).