
PXB 4330
Functional Description
Data Sheet
3-48
09.99
3.1.8
The ABM chip provides several statistical counters for maintenance purposes.
Statistical Counters
Global Counters:
Total stored cells upstream and downstream
Total stored non-real-time cells upstream and downstream
Per Traffic Class Counters:
Accepted packets
Discarded packets or discarded CLP = 1 cells
Total discarded cells
Discarded cells due to scheduler overflow
Discarded cells due to traffic overflow
In addition, two types of sample-hold registers are provided:
Minimum buffer occupancy value since last readout upstream and downstream
Maximum buffer occupancy value since last readout upstream and downstream
3.1.9
Supervision Functions
3.1.9.1
To guarantee that the cell header is not corrupted by the external SDRAM, it is protected
by a 8-bit interleaved parity octet. It extends over the 5-octet standard header including
the UDF1 octet. The BIP-8 octet is calculated for all incoming cells and stored at the
place of the UDF2 octet. When a cell is read out, the BIP-8 is calculated again and is
compared with the stored BIP-8. In case of a mismatch, an interrupt is signaled and the
cell is discarded or not, depending on the configuration.
Note: Due to the usage of the UDF2 field for the BIP-8, the UDF2 octet is not transparent
through the ABM.
Cell Header Protection
3.1.9.2
The queuing of cells in the ABM is implemented mostly by pointers. To detect pointer
errors, the number of the queue in which the cell is stored is appended to the cell in the
external cell storage SDRAM. When the cell is read out later, the selected queue number
is compared to the QID stored with the cell. In case of a mismatch, an interrupt is
signaled.
Cell Queue Supervision