mt90528ag2 Zarlink Semiconductor, mt90528ag2 Datasheet - Page 78

• Manufacturer Part Number: mt90528ag2
• Description: 28-port Primary Rate Circuit Emulation Aal1 Sar
• Manufacturer: Zarlink Semiconductor

Here are some examples of incoming cell streams containing errors and the corresponding corrective actions taken
by the SDT RX_SAR.
4.6.1.5
The RX_SARs are responsible for extracting data from received cells and transferring that data to the TDM module,
for eventual transmission onto the TDM output bus. In addition, these modules are responsible for:
•
•
•
•
Sequence number protection
failure (looks like single cell
loss)
Sequence number protection
failure (looks like multiple cell
loss)
Single lost cell
Multiple lost cells (from 2 to 6
lost cells)
Misinserted (swapped) cell
NOTE: D indicates the insertion of a dummy cell containing user-programmable data.
performing slip checking and RX_SAR write-pointer adjustment prior to transferring data to the TDM module
generating dummy cells in the case of sequence errors such as lost or misinserted cells
SDT pointer processing
extracting CAS from SDT cells and transferring it to the TDM module
Description of Error
out_of_seq
Current State
Table 18 - Examples of Operation of SDT Fast Sequence Number Processing State Machine
Received Cell Processing
Table 17 - Operation of SDT Fast Sequence Number Processing State Machine
invalid sequence number
received cell is in sequence with last “good”
cell (i.e., cell misinsertion)
received cell is in sequence with last received
cell (i.e., cell loss)
received cell has a valid sequence number
that is two greater than the last in-sequence
cell (i.e., sequence number protection failure)
received cell has valid sequence number, but
doesn’t meet any of the 3 previous criteria
Sample Incoming Cell
Transition Event
1 - 2 - 4 - 3 - 5 - 6
1 - 3* - 3 - 4 - 5
1 - 4* - 3 - 4 - 5
1 - 2 - 4 - 5
1 - 2 - 6 - 7
Stream
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MT90528
78
1 - 2 - 6 - D
- discard cell
- discard cell (because misinserted
cell was accepted when it shouldn’t
have been)
- declare misinserted_cell_error
- calculate number of lost cells (up
to 6)
- SDT RX_SAR inserts dummy
cell(s)
- after dummy cell insertion(s),
accept received cell
- declare lost_cell_error
- accept received cell
- discard cell
Cells Used for
1 - 2 - 4 - 5 - D
Reassembly
1 - 2 - 4 - D
1 - 3* - 3 - 4 - 5
1 - 4* - 3 - 4 - 5
Action Taken
3
- D
3
4
- 5
- D
4
- 6
5
- 7
1 AAL1 Sequence Error
1 AAL1 Sequence Error
1 AAL1 Sequence Error
1 Lost Cell
1 AAL1 Sequence Error
3 Lost Cells
2 AAL1 Sequence Errors
1 Misinserted Cell
1 Lost Cell
Errors Declared
start
sync
sync
sync
out_of_sync
Next State
Data Sheet