DP83251 datasheet(11/96 Pages) NSC

11 / 96 page

30 Functional Description (Continued)

33 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

The Configuration Switch has four internal buses

the

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

PHY Port Interface output data paths A

Indicate and

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-

5a ) The DP83251 having only one port interface uses the

Request and A

Indicate paths as its external port The

Request and B

Indicate paths of the DP83251 are null

connections and are not used by this device (see

Figure 3-

5b )

TLF10386 – 7

FIGURE 3-5a Configuration Switch Block

Diagram for DP83255

TLF10386 – 34

FIGURE 3-5b Configuration Switch Block

Diagram for DP83251

DP83251 Datasheet(PDF) 11 Page - National Semiconductor (TI)

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