XRT75L00D Datasheet, PDF (57/92 Pages) Exar Corporation – E3/DS3/STS-1 LINE INTERFACE UNIT WITH SONET DESYNCHRONIZER

REV. 1.0.2
XRT75L00D
E3/DS3/STS-1 LINE INTERFACE UNIT WITH SONET DESYNCHRONIZER
FIGURE 33. THE BYTE-FORMAT OF THE TOH WITHIN AN STS-1 FRAME
9 Rows
3 Byte Columns
87 Byte Columns
AA11
BB11
DD11
HH11
BB22
DD44
DD77
DD1100
SS11
AA22
EE11
DD22
HH22
KK11
DD55
DD88
DD1111
MM00
CC11
FF11
DD33
HH33
KK22
DD66
DD99
DD1122
EE22
EEnnvveellooppeeCCaappaacciittyy
BByytteess
The TOH Bytes
In general, the role/purpose of the TOH bytes is to fulfill the following functions.
• To support STS-1 Frame Synchronization
• To support Error Detection within the STS-1 frame
• To support the transmission of various alarm conditions such as RDI-L (Line - Remote Defect Indicator) and
REI-L (Line - Remote Error Indicator)
• To support the Transmission and Reception of "Section Trace" Messages
• To support the Transmission and Reception of OAM&P Messages via the DCC Bytes (Data Communication
Channel bytes - D1 through D12 byte)
The roles of most of the TOH bytes is beyond the scope of this Data Sheet and will not be discussed any
further. However, there are a three TOH bytes that are important from the stand-point of this data sheet, and
will discussed in considerable detail throughout this document. These are the H1 and H2 (e.g., the SPE
Pointer) bytes and the H3 (e.g., the Pointer Action) byte.
Figure 34 presents an illustration of the Byte-Format of the TOH within an STS-1 Frame, with the H1, H2 and
H3 bytes highlighted.
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