NEC UPD98413 User Manual page 47

OOF If a frame synchronization pattern cannot be
α
detected in forward protection stages in a row.
LOF If the OOF status lasts for 3 ms.
If the LOFDT
LOF status is detected at the same time as OOF.
LOS If the signals input to RDIT do not change in level
µ
for 25 s (if the CDO bit of the MDSOHR register
is 1, the LOS status is reported when the CD pin
goes low.)
(2) Descramble of receive frame
After frame synchronization has been established, the received frame is descrambled with the polynomial shown
below. The entire range of the STS-12c frame, except the 36 bytes from the beginning, "A1 (12), A2 (12), J0 (1),
Z0 (11)" is descrambled.
Polynomial G (X) = 1 + X
An option mode that disables descrambling of a frame is provided for testing purposes. This mode is set by
using the FSCM Bit of the MDSOHR register.
CHAPTER 3 FUNCTIONAL OUTLINE
Table 3-2. OOF, LOF, and LOS Detection Conditions
Detection Condition
bit of the MDSOHR register is 0, the
6 7
+ X
PRELIMINARY
Termination Condition
If a frame synchronization pattern is detected
backward protection stages in a row
If the µPD98413 is not in the OOF status for 3 ms.
If the LOFDT bit of the MDSOHR register is 0, the
LOF status is terminated at the same time as OOF.
The µPD98413 is able to select the LOS termination
condition, Bellcore mode or ANSI mode, by the LOST
bit of the MDSOHR register.
Bellcore Mode:
If the incoming signal has two consecutive valid
framing alignment patterns, and no pulse-free
intervals for 25µ s consecutive time between that tow
consecutive valid framing.
ANSI Mode:
If the incoming signal that have no pulse-free
µ µ
intervals of 25 s for 125 s.
*If the CD pin is High for above termination condition
25µ s consecutive time. (If include CD pins input for
this termination condition (CDO bit of the MDSOHR
register is 1),)
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δ
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