XRT75VL00D datasheet(67/92 Pages) EXAR

67 / 92 page

XRT75VL00D

REV. 1.0.3

E3/DS3/STS-1 LINE INTERFACE UNIT WITH SONET DESYNCHRONIZER

Figure 43 relates the contents within these 10 bits (within the H1 and H2 bytes) to the location of the J1 byte

(e.g., the very first byte of the STS-1 SPE) within the Envelope Capacity.

NOTES:

If the content of the "Pointer Bits" is "0x00" then the J1 byte is located immediately after the H3 byte, within the

Envelope Capacity.

If the contents of the 10-bit expression exceed the value of 0x30F (or 782, in decimal format) then it does not

contain a valid pointer value.

9.3.2

Pointer Adjustments within the SONET Network

The word SONET stands for "Synchronous Optical NETwork.

This name implies that the entire SONET

network is synchronized to a single clock source. However, because the SONET (and SDH) Networks can

FIGURE 42. THE BIT-FORMAT OF THE 16-BIT WORD (CONSISTING OF THE H1 AND H2 BYTES) WITH THE 10 BITS,

REFLECTING THE LOCATION OF THE

J1 BYTE, DESIGNATED

FIGURE 43. THE RELATIONSHIP BETWEEN THE CONTENTS OF THE "POINTER BITS" (E.G., THE 10-BIT EXPRESSION

WITHIN THE

H1 AND H2 BYTES) AND THE LOCATION OF THE J1 BYTE WITHIN THE ENVELOPE CAPACITY OF AN STS-

1 FRAME

LSB

MSB

H2 Byte

H1 Byte

10 Bit Pointer Expression

521

520

* * * * * * * *

* *

436

435

434

433

* * * * * * * *

* *

349

348

D12

D11

D10

347

346

* * * * * * * *

* *

262

261

260

259

* * * * * * * *

* *

175

174

173

172

* * * * * * * *

* *

* * * * * * * *

* *

782

781

* * * * * * * *

* *

697

696

695

694

* * * * * * * *

* *

610

609

608

607

* * * * * * * *

* *

523

522

C1/J0

TOH

The Pointer Value “0” is immediately

After the H3 byte

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