PXB4219E Datasheet, PDF (61/290 Pages) Infineon Technologies AG – Interworking Element for 8 E1/T1 Lines

IWE8, V3.4
PXB 4219E, PXB 4220E, PXB 4221E
Operational Description
The number of memory blocks used depends on the bandwidth of the channel (N*64-
kbit/s). Thus for structured CES with N*64-kbit/s there are N x 8 memory blocks per
connection.
The one-to-one relationship between timeslots and groups of memory blocks allows
dynamic re-configuration of a specific channel without disturbing other channels of the
same port.
4.4.1.9 Handling of Reassembly Buffer Overflow
Overflow is detected when, at the moment of storing an accepted cell, the extra payload
of the new cell in the buffer would exceed the logical size of the Reassembly Buffer.
For AAL type 1 two possible actions exist:
• The cell is discarded.
Re-initialization of the Reassembly Buffer as described in Chapter 4.4.2.4 is in line
with the ITU-T I.361.1 [31]
• The cell is accepted but the Reassembly Buffer is automatically re-initialized.
Re-initialization is done automatically without disturbing the microprocessor.
The action chosen is determined by the “auto_reinit_of” field in the “AAL Transmit
Reference Slot” in RAM3.
When using AAL type 0, the accepted cell is considered to be a misinserted cell and
rejected.
4.4.1.10 Handling of Reassembly Buffer Underflow
An underflow period is detected when no octets are available in the Reassembly Buffer
to be passed to the framer transmit interface. During the underflow period starvation
octets are passed to the framer transmit interface and Statistics Counter 12 increments
if enabled.
For AAL type 1, the underflow is considered to be caused by an extremely late cell. The
length of the underflow period is measured by counting the number of transmitted
starvation octets, expressed as a number of starvation cells that are counted by
Statistics Counter 13 if enabled
For resolving the underflow two possibilities exist:
• Manual re-initialization:
Re-initialization of the Reassembly Buffer as described in Chapter 4.4.2.4 is in line
with the ITU-T I.361.1 [31]
• Automatic re-initialization:
As soon as start of underflow is detected, the Reassembly Buffer is re-initialized
without disturbing the microprocessor. Thus, the underflow status for the device is no
longer valid although the underflow condition still exists. No starvation cells due to
underflow will be inserted and counter 13 will not increment
Data Sheet
61
2003-01-20