NEC UPD98413 User Manual page 62

• The hunting status is that status in which synchronization is not established and a cell boundary is searched.
A check of whether an HEC error has occurred is made (CRC (Cyclic Redundancy Check) is conducted with
1 bit each shifted to check whether the remainder is 0.) If HEC coincides and an HEC with no errors is
detected, the status changes to the preceding synchronization status.
• In the preceding synchronization (PRESYNC) status, the candidate of a cell boundary is found in the hunting
(HUNT) status, and whether this candidate is correct is checked. The µ PD98413 enters the cell
synchronization status when it has received HEC without an error
status if detects an HEC error. The
the receive FIFO, starting from the next cell.
• The cell synchronization status (SYNC) is the normal status in which cell synchronization is established. If an
HEC error is detected
the µ PD98413 enters the hunting status.
• The number of forward protection stages (
δ
= 6 in the default mode. However,
δ
and can be changed by setting the OCDT[1:0] bits.
Table 3-9. Number of Forward/Backward Protection Stages of Cell Synchronization
Number of Forward
Protection Stages
6
7 (default)
8
9
• The status in which cell synchronization is not established is reported as the Out Of Cell Delineation (OCD)
status. If this status lasts for 4 ms, the µ PD98413 enters the Loss Of Cell Delineation (LCD) status. The LCD
status is cleared if the cell synchronization status lasts for 4 ms. The 4 ms required to detect and clear the
LCD status can be changed to 0 ms by using the LCDDT bit of the MDATMR register to make the condition of
detecting and terminating OCD and LCD the same.
OCD If normal HEC cannot be detected in
forward protection stages in a row.
LCD If OCD lasts for 4 ms.
If the LCDDT bit of the MDATMR register
is 0, the LCD status is detected at the
same time as OCD.
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CHAPTER 3 FUNCTIONAL OUTLINE
δ
th cell that is free from an error is dropped, and the cells are stored to
α
times in a row, it is considered that cell synchronization is no longer established and
α
) and the number of backward protection stages (
α
can be changed by setting the OCDD[1:0] bits of the MDATMR register
MDATMR Register
α
OCDD[1:0]
00
01
10
11
Table 3-10. OCD and LCD Detection Conditions
Detection Condition
α
PRELIMINARY
δ
times in a row. It returns to the hunting
Number of Backward MDATMR Register
δ
Protection Stages
5
6 (default)
7
8
Termination Condition
If normal HEC is detected in
protection stages + 1 in a row.
If cell synchronization status lasts for 4 ms.
If the LCDDT bit of the MDATMR register
is 0, the LCD status is cleared at the same
time as OCD.
NEC confidential and Proprietary
δ α
) are = 7 and
OCDT[1:0]
00
01
10
11
δ
backward