XRT75R03D_06 Datasheet, PDF (98/135 Pages) Exar Corporation – EXAR DATA SHEET FORMAT TEMPLATES

XRT75R03D
THREE CHANNEL E3/DS3/STS-1 LINE INTERFACE UNIT WITH SONET DESYNCRONIZER
REV. 1.0.4
FIGURE 33. A SIMPLE ILLUSTRATION OF THE STS-1 FRAME STRUCTURE WITH THE TOH AND THE ENVELOPE
CAPACITY BYTES DESIGNATED
3 Bytes
90 Bytes
87 Bytes
TOH
Envelope Capacity
9 Row
Since the TOH bytes occupy the first three byte columns of each STS-1 frame, and since each STS-1 frame
consists of nine (9) rows, then we can state that the TOH (within each STS-1 frame) consists of 3 byte columns
x 9 rows = 27 bytes. The byte format of the TOH is presented below in Figure 34.
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