Technical data

(11) Link Lockup Protection

During the reception of 10BASE-T data, the link partner may switch to 100BASE-TX without starting

auto-negotiation. In this case, the PHY must recognize this, de-assert the link status, and switch to

100BASE-TX mode.

To achieve this, a counter is activated at the beginning of every 10BASE-T packet. When the counter

reaches the count of 157 msec and no end of packet was recognized, then the link will be de-asserted

and the PHY will restart either auto-negotiation (if enabled) or try to achieve a 10BASE-T link again.

(12) Phase Offset Indicator

The latency between transmitter and receiver can lead to 5 different phase variations of 125Mbps

received packets against the 25Mbps data on the MII interface (only in 100BASE-TX/FX mode). It cor-

responds to the system latency between MII TX_EN_P(2:1) and MII RX_DV_P(2:1) and it is measured

based on the first packet after link-up. This value is then stored in the PHASE_OFFSET field of the

Special Controls/Status Indications register.

Figure 4 illustrates this function.

Figure 4: Phase Offset Indicator Function

Technical data subject to change Version 1.0.0