PXB4220E Infineon Technologies AG, PXB4220E Datasheet - Page 65

• Manufacturer Part Number: PXB4220E
• Description: Interworking Element for 8 E1/T1 Lines
• Manufacturer: Infineon Technologies AG

As the transmission of the reassembled cell stream is delayed by “starv_ini”+1 octets,
there will be “starv_ini”+1 octets of the previous cell left in the Reassembly Buffer if the
following cell arrives without CDV.
If the maximum positive CDV is the same as the maximum negative CDV the expectation
interval has a length of 2 x CDV. Assuming N octets of data are transmitted within one
frame period of 125µs the amount of data transmitted in this interval is:
The worst case for buffer underflow is given if the first cell has maximum positive CDV.
Figure 16
In this case the amount of starvation octets inserted after receipt of the first cell has to
be bigger than the amount of data transmitted during the expectation interval. Otherwise
the Reassembly Buffer will enter underflow condition at any time a cell with maximum
positive CDV is followed by a cell with maximum negative CDV.
The worst case for buffer overflow is given if the first cell has maximum negative CDV
and then any cell with maximum negative CDV is followed by a cell with maximum
positive CDV.
Data Sheet
Framer
starvini
4
0
Interf.
=
Filling Level [octets]
Reassembly Buffer
buff_lsize
2
Starvation octets
Data octets
CDV
T
0
T
-CDV
–
0
Reassembly Buffer Initialization: positive CDV at Start Up
1
T
0
=
-CDV+T
-------------- -
125 s
2
N
CDV
S
T
T
T: Average cell distance
0
S
: First cell arrival time (theoretical)
: (starv_ini + 1) * 125µs / N
-------------- - 1
125 s
N
T
0
–
+T
Example: part_fill = 16 octets; N = 16
1st cell has max. pos. CDV = 15,625µs
2nd cell has max. neg. CDV = -15,625µs
T
0
65
0
+T+CDV
PXB 4219E, PXB 4220E, PXB 4221E
T
T
Operational Description
0
0
+2*T
+2*T-CDV
Reassembly Buffer pos CDV
IWE8, V3.4
2003-01-20
Time
Time
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