Ethernet Physical Transceiver (EPHY)
MCF52235 ColdFire® Integrated Microcontroller Reference Manual, Rev. 6
Freescale Semiconductor
19-25
19.4.2
Auto-Negotiation
Auto-negotiation is used to determine the capabilities of the link partner. Auto-negotiation is compliant
with IEEE 802.3 clause 28. In this case, the PHY transmits fast link pulse (FLP) bursts to share its
capabilities with the link partner.
If no common mode is found, the remote fault bit (1.4) is set. A remote fault is defined as a condition in
which the PHY and the link partner cannot establish a common operating mode. Configuring
auto-negotiation advertisement register sets the different auto-negotiation advertisement modes.
If the link partner does not support auto-negotiation, it transmits normal link pulses (NLP) for 10 Mbps
operation or 100 Mbps idle symbols. Based on the received signal, the PHY determines whether the link
partner is 10 Mbps capable or 100 Mbps capable. The ability to do this is called parallel detection. If using
parallel detection, the link is configured as a half-duplex link. After parallel detection has established the
link configuration, the remote fault bit is set if the operating mode does not match the pre-set operating
modes.
shows the main blocks used in the auto-negotiation function. The transmit block allows
transmission of fast link pulses to establish communications with partners that are auto-negotiation able.
The receive block determines the capabilities of the link partner and writes to the link partner ability
register (register 5). The arbitration block determines the highest common mode of operation to establish
the link.
Because
of
an
order
from
the
United
States
International
Trade
Commission,
BGA-packaged
product
lines
and
part
numbers
indicated
here
currently
are
not
available
from
Freescale
for
import
or
sale
in
the
United
States
prior
to
September
2010:MCF52234CVM60,
MCF52235CVM60
