PXB4219E Datasheet, PDF (55/290 Pages) Infineon Technologies AG – Interworking Element for 8 E1/T1 Lines

IWE8, V3.4
PXB 4219E, PXB 4220E, PXB 4221E
Operational Description
4.3.1.6 Segmentation Buffer
The Segmentation Buffer is located in external RAM providing 256 bytes of memory for
each timeslot, totalling to 64 KB for 8 ports with 32 timeslots each. The buffer for each
timeslot consists of 4 blocks with 64 octets:
Buffer size = 8 Ports x 32 Channels x 4 Blocks x 64 Octets
[1]
In unstructured CES mode, one Segmentation Buffer per port provides 16 blocks.
In structured CES mode, a Segmentation Buffer per channel with a variable capacity
depending on the number of channels and the cell filling level is automatically configured
by the IWE8. The number of memory blocks depends on the bandwidth of the channel.
Thus for structured CES with N x 64-kbit/s there are N x 4 blocks per connection. Each
channel can occupy 1, 2 or 4 block-groups (4, 8 or 16 blocks). The first block-group
defines the reference slot number of the channel. The second, third and fourth block-
groups define the number of the corresponding interface slot of the channel.
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.
Table 16
Cell Filling
AAL0
(octets)
25-48
4-24
Relationship betw. Cell Filling & Segmentation Buffer Subblock Size
Cell Filling
AAL1, no
SDT
(octets)
Cell Filling
AAL1, with
SDT
(octets)
Octets per
block
Cells per
block
Octets per
cell
25-47
25–47
64
1
64
4-24
4–24
64
2
32
4.3.1.7 Padding Partially Filled Cells
The value, used for dummy fill of partially filled cells, is programmable in the Cell Fill
Register for Partially Filled Cells (“cfil”, see Chapter 7.12). The fill octets carry no
information and are ignored at the receiver.
Table 17 shows valid values for the cell filling level, which can be configured in the field
part_fill of RAM1: AAL Receive Reference Slot (see Chapter 6.1.1.3) and RAM2: AAL
Transmit Reference Slot (see Chapter 6.1.2.3). All other values are illegal.
Data Sheet
55
2003-01-20