DP83256 datasheet(18/144 Pages) NSC

18 / 144 page

30 Functional Description (Continued)

34 CONFIGURATION SWITCH

The Configuration Switch consists of a set of multiplexers

and latches which allow the PLAYERa device to configure

the data paths without any external logic The Configuration

Switch is controlled through the Configuration Register

(CR)

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 PLAYERa device while the

PHY

Invalid bus has a fixed 10-bit SMT PHY Invalid con-

nection (LSU) pattern (1 0011 1010) which is useful during

the connection process

The configuration switch also has three internal multiplex-

ers 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 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 the DP83256 de-

vice the DP83256-AP device and the DP83257 device

However the DP83257 has two PHY Port interfaces con-

nected to the Configuration Switch whereas the DP83256

and DP83256-AP have one set of PHY port interfaces The

DP83257 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 3-8 )

The DP83256 and DP83256-AP having one port interface

use the B

Request and A

Indicate paths as its external

port

The A

Request and B

Indicate paths of the

DP83256 and DP83256-AP are null connections and are not

used by the device (See

Figure 3-9 )

TLF11708 – 11

FIGURE 3-8 Configuration Switch

Block Diagram for DP83257

TLF11708 – 12

FIGURE 3-9 Configuration Switch

Block Diagram for DP83256

and DP83256-AP

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