PXB4219E Datasheet, PDF (66/290 Pages) Infineon Technologies AG – Interworking Element for 8 E1/T1 Lines

Reassembly Buffer
Filling Level [octets]
buff_lsize
IWE8, V3.4
PXB 4219E, PXB 4220E, PXB 4221E
Operational Description
Example: part_fill = 16 octets; N = 16
1st cell has max. neg. CDV = 15,625µs
2nd cell has max. pos. CDV = -15,625µs
4
0
Framer
Interf.
T₀
T₀+CDV+T_S
T₀+CDV
T₀+T
T₀+T-CDV
T₀: First cell arrival time (theoretical)
Starvation octets
T_S: (starv_ini + 1) * 125µs / N
Data octets
T: Average cell distance
T₀+2*T
T₀+2*T+CDV
Time
Time
Reassembly Buffer neg CDV
Figure 17 Reassembly Buffer Initialization: Negative CDV at Start Up
If the first cell has maximum negative CDV there will be “starv_ini” + 1 octets left in the
Reassembly Buffer when 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:
bufflsize ≥ partfill + starvini + 1 + ∆= partfill + 4 × CDV × _{1---2---N-5---µ}----s
[6]
The delay introduced by the Reassembly Buffer is:
delay= ^{s---t--a---r---v---i--n---i----×}----1---2---5----^µ---s-
[7]
N
Structured Data Transfer:
After activation of a channel both SAR Receiver and Framer Transmit Interface start
operation. As long as no reassembled cell in P format is accepted the Reassembly Buffer
it is considered to be in underflow condition and starvation octets are passed to the
Framer Transmit Interface.
After that, “starv_ini” + 1 starvation octets are given to the Framer Transmit Interface.
Then, the transmitter reads as many octets from the Reassembly Buffer as indicated by
the pointer field. For each octet one starvation octet is given to the Framer Transmit
Interface. The next octet to be read from the Reassembly Buffer is the “ATM Start of
Structure” (The octet where the AAL1 pointer field points at).
Data Sheet
66
2003-01-20