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Datasheet 19
Networking Silicon — 82555
The figure below illustrates an 82557/82555/PHY-T4 solution in a block diagram.
4.6 Auto 10/100 Mbps Speed Selection
The MAC may either allow the 82555 to automatically select its operating speed or force the 82555
into 10 Mbps or 100 Mbps mode. The Management Data Interface (MDI) can control the 82555
speed mode.
The 82555 autoselect function determines the operation speed of the media based on the link
integrity pulses it receives. If no Fast Link Pulses (FLPs) are detected and Normal Link Pulses
(NLPs) are detected, the 82555 defaults to 10 Mbps operation. If the 82555 detects a speed change,
it dynamically changes its transmit clock and receive clock frequencies to the appropriate value.
This change takes a maximum of five milliseconds.
4.7 Adapter Mode Addresses
In DTE (adapter) mode, the 82555 supports addresses 0, 1, 2, and 3 through the pins PHYA1 and
PHYA0. Four addresses are sufficient in the case of a combination adapter having three PHYs. For
switch applications, the T4ADV signal should be de-asserted to allow all 32 addresses to be
available in repeater mode.
Figure 8. Combination Card Example
Common
Magnetics
PCI BUS
82557
fdx_n
PHY-T4
82555
T4
adv
MII
listat_n
slave_tri
3669