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How Frames are Generated How the Frame Generator Works
Agilent 81250 ParBERT SONET/SDH Frame Generator, November 2002 19
Single B1 Error The user can specify a single B1 error per frame.
To generate a B1 error (for channel 1 only), one 1 of a selected byte is
complimented (the byte is XORed with
0000 0001
).
The selected byte is located at channel 1 (SONET) or channel 1-a
(SDH), row 3, column 1. This byte is unused by the signal.
The B1 byte itself remains unchanged.
Framing
A complete framing pattern (3, 12, 48, 192, 768 x F6 + 3, 12, 48, 192,
768 x 28) is generated.
Out Of Frame (OOF)
Out Of Frame is generated by inverting the first A1 byte (F6 becomes
09), and the first A2 byte (28 becomes D7).
J0/Z0 Section Trace/Growth Bytes
For SONET, the STS-768 ID J0 byte will always be 1.
For SDH, the STM-256 ID J0 bytes will be numbers 1, 2, 3 to 0.
For SDH, the undefined Z0 bytes will be set to
AA
(
1010 1010
) (the
physical sequence will be: 1, 2, 3, 4, ... 255, 0, AA, AA, ... AA, AA).
Similar numbering applies to all other frames.
All Other Section Overhead
All other section overhead bytes will contain
0000 0000
prior to
scrambling, except the D1, D2 and D3 bytes, which are used for
synchronizing.