dp83251 National Semiconductor Corporation, dp83251 Datasheet - Page 11

• Manufacturer Part Number: dp83251
• Description: Player Device Fddi Physical Layer Controller
• Manufacturer: National Semiconductor Corporation

3 0 Functional Description
3 3 CONFIGURATION SWITCH
The Configuration Switch consists of a set of multiplexors
and latches which allow the PLAYER device to configure
the data paths without the need of external logic The Con-
figuration Switch is controlled through the Configuration
Register (CR)
The Configuration Switch has four internal buses the
A Request bus the B Request bus the Receive bus and
the PHY Invalid bus The two Request buses can be driv-
en by external input data connected to the external PHY
Port Interface The Receive bus is internally connected to
the Receive Block of the PLAYER device while the PHY
Invalid bus has a fixed 10-bit LSU pattern useful during the
connection process The configuration switch also has three
internal multiplexors each can select any of the four buses
to connect to its respective data path The first two are
FIGURE 3-5a Configuration Switch Block
Diagram for DP83255
(Continued)
TL F 10386 – 7
11
5a ) The DP83251 having only one port interface uses the
5b )
PHY Port Interface output data paths A Indicate and
B Indicate that can drive output data paths of the external
PHY Port Interface The third output data path is connected
internally to the Transmit Block
The Configuration Switch is the same on both the DP83251
device and the DP83255 device However the DP83255
has two PHY Port interfaces connected to the Configuration
Switch whereas the DP83251 has one PHY Port Interface
The DP83255 uses the A Request and A Indicate paths
as one PHY Port Interface and the B Request and B Indi-
cate paths as the other PHY Port interface (see Figure 3-
B Request and A Indicate paths as its external port The
A Request and B Indicate paths of the DP83251 are null
connections and are not used by this device (see Figure 3-
FIGURE 3-5b Configuration Switch Block
Diagram for DP83251
TL F 10386 – 34