DP83256 datasheet(33/144 Pages) NSC

33 / 144 page

40 Modes of Operation (Continued)

Long Internal Loopback

The Long Internal Loopback mode implements the longest

loopback path that is completely within the PLAYERa de-

vice

The Long Internal Loopback mode can be used to test the

functionality of the PLAYERa device including the Clock

Recovery function and to test the data paths between the

PLAYERa device and MACSI devices before ring insertion

When in the Long Internal Loopback mode the PLAYERa

device performs the following functions

Directs the output data of the Transmitter Block to the

input of the Clock Recovery Module through an internal

path

Ignores the PMD Data Indicate pins (PMIDg)

Outputs Quiet symbols through the PMD Data Request

pins (PMRDg)

The level of the Quiet symbols transmitted through the

PMRDg pins during loopback is automatically set to the

transmitter off level

If both Short Internal Loopback and Long Internal Loopback

modes are selected Long Internal Loopback mode will

have priority over Short Internal Loopback mode This is the

longest loopback path within the PLAYERa device

Note that the LILB path is disconnected and should not be

used when the Alternate PMD Interface is active

See

Figure 4-4 Long Internal Loopback

TLF11708 – 26

FIGURE 4-4 Long Internal Loopback

DP83256 Datasheet(PDF) 33 Page - National Semiconductor (TI)