DP83256VF datasheet(29/144 Pages) NSC

29 / 144 page

30 Functional Description (Continued)

38 PMD INTERFACE

The PMD Interface connects the PLAYERa device to a

standard FDDI Physical Media Connection such as a fiber

optic transceiver or a copper twisted pair transceiver It is a

125 MHz full duplex serial connection

The DP83256 PLAYERa device contains one PMD inter-

face This PMD Interface should be used for all PMD imple-

mentations that do not require an external scrambler

descrambler function clock recovery function or clock

generation function such as a Fiber Optic or Shielded

Twisted Pair (SDDI) PMDs

The DP83256-AP and DP83257 PLAYERa devices contain

two PMD interfaces The PMD Interface should be used for

all PMD implementations that do not require an external

scramblerdescrambler function clock recovery function

or clock generation function such as a Fiber Optic or

Shielded Twisted Pair (SDDI) PMDs The second Alternate

PMD Interface can be used to support Unshielded Twisted

Pair (UTP) PMDs that require external scrambling and al-

lows implementation with no external clock recovery or

clock generation functions required See

Figure 3-21

PLAYERa TO PMD CONNECTIONS

The following figures illustrate how the PLAYERa device

can be connected to various types of PMDs

Figure 3-20 shows how the DP83256 DP83256-AP or

DP83257 PLAYERa device is connected to a Fiber Optic

or Shielded Twisted Pair (SDDI) PMD using the Primary

PMD Interface

Figure 3-21 shows how the DP83256-AP or DP83257

PLAYERa device is connected to an Unshielded Twisted

Pair (UTP) PMD using the Alternate PMD Interface

TLF11708 – 47

FIGURE 3-20 Fiber Optic or STP PMD Connection

TLF11708 – 48

FIGURE 3-21 UTP PMD Connections

DP83256VF 데이터시트(PDF) 29 Page - National Semiconductor (TI)