PXB4219E Datasheet, PDF (62/290 Pages) Infineon Technologies AG – Interworking Element for 8 E1/T1 Lines

IWE8, V3.4
PXB 4219E, PXB 4220E, PXB 4221E
Operational Description
The action chosen is determined by the “auto_reinit_uf” field in the “AAL Transmit
Reference Slot” in RAM3.
For AAL type 0 the detection of an underflow period is considered to be the detection of
cell loss. For this reason a dummy cell is inserted. The inserted dummy cell must be
reflected in the buffer filling level of the Reassembly Buffer.
4.4.1.11 Synchronization of SDT Structure with Port Structure
In normal operation the “ATM start of structure” is synchronized with the “Port start of
structure”. Since this synchronization may get lost, the coincidence of both events is
monitored. If they do mismatch, a two bit error counter is incremented. Upon reaching a
programmable threshold, the Reassembly Buffer is re-initialized and Statistics Counter
14 is incremented if enabled. The threshold value is programmed in the “sdt_oos_nr”
field of the “AAL Transmit Reference Slot” in RAM2. If the Statistics Counter 14 should
reflect “atmfCESPointerReframes” as defined in [10], “sdt_oos_nr” should be set to
“00”.
To compensate cell loss the Sequence Count algorithm inserts dummy cells filled with
starvation octets. In case the cell filling level is 46 octets or less, the bit count integrity
won’t be violated as the length of the AAL-user information within one SAR-SDU is
always the same. When operating with a cell-filling of 47 octets, the AAL-user
information maybe 47 octet in case of non-P format or 46 octet in case of P format SAR-
PDU. As the information on the lost cell’s SAR-PDU format is not available, it is possible
that an excess of starvation octets is transmitted. As a result, the “ATM start of structure”
might be out of phase with the “Port start of structure”.
The following procedure is implemented for re-synchronization:
• At the end of expanding a burst of dummy cells a flag is set, indicating that a phase
shift might occur. The maximum phase shift is 2 octets (e.g. 2 cells with pointers are
lost within a sequence of eight cells)
• When an “ATM start of structure” is received and a positive phase shift is detected
lower than or equal to 2 octets, an equal number of octets is deleted in the
Reassembly Buffer and the flag is reset.
• When the detected phase shift is larger than the allowed value or negative the flag is
reset and the Reassembly Buffer is re-initialized.
• When no phase shift is detected the flag is reset.
4.4.2 Setup
4.4.2.1 Setup of Reassembly Channels
Each AAL transmit channel can be configured in the “channel_mode” field of the “AAL
Transmit Reference Slot” to operate in “Inactive”, “Standby” or “Active” mode.
Data Sheet
62
2003-01-20