PXB4219 Datasheet, PDF (71/290 Pages) Infineon Technologies AG – IWE8 Interworking Element for 8 E1/T1 Lines

PXB4219 / PXB4220 / PXB4221
Operational Description
with maximum negative CDV. the following cell arrives with maximum negative CDV. In
case the following cell arrives with maximum positive CDV it will be “starv_ini” + 1 plus
the amount of data to be transmitted in the expectation interval. Just after cell arrival the
filling level of the Reassembly Buffer is at its maximum:
To allow CDV compensation and SDT structure synchronization, the logical size should
be programmed to a minimum value given by:
bufflsize ≥ partfill + starvini + 1 + ∆ + FR × N + Pmax
[9]
bufflsize ≥ partfill + 4 × CDV × -1---2--N-5---_µ----s + FR × N + Pmax
[10]
with FR being the number of frames in a structure:
FR = 0: when SDT is not used
FR = 1: for frame based SDT
FR = 16: for multi-frame based SDT in E1 mode
FR = 24: for multi-frame based SDT in T1 mode
Pmax is the maximum number of payload octets from the pointer field to the start of
structure:
Pmax = N x FR, if N x FR < 2 x part_fill
Pmax = 2 x part_fill, if N x FR > 2 x part_fill
The logical Reassembly Buffer size is limited by its physical size. The relation is given by:
bufflsize ≤ 8 × N × partfill × cellsperblock – S × partfill
[11]
where
S = 0: in case of Fast Sequence Count Algorithm
S = 1: in case of Robust Sequence Count Algorithm
When the robust SC algorithm is used, the decision on cell acceptance is delayed until
the next cell is received. As the cell is temporarily stored in the Reassembly Buffer, there
must always be space for that cell. Therefore, the physical size of the Reassembly Buffer
must be at least the logical size plus one cell.
In the fast SC algorithm the intermediate storage of a cell is not required. The cell is
stored immediately in the Reassembly Buffer, when accepted.
The delay introduced by the Reassembly Buffer is:
s---t--a---r---v---i--n---i----×_{----1---2---5----}µ_---s-
N
≥
d
e
lay
≤
(_{---s---t--a---r--v---i--n----i---+-----F---R------}×_{-----N------+-----P---m-----a---x----})_---×_{-----1---2---5---}µ_----s-
N
[12]
Data Sheet
71
2002-05-06