pxf4333 Infineon Technologies Corporation, pxf4333 Datasheet - Page 108

• Manufacturer Part Number: pxf4333
• Description: Abm 3g Atm Buf Fer Manager
• Manufacturer: Infineon Technologies Corporation

the delivered CCR
the desired CCR
Table 4-3
Desired CCR
[cells/s]
4830
353108
1412429
The deviation of the delivered CCR from the desired CCR is always less than 1
improves towards lower CCR.
Scheduler Block Burst Limitation
Per scheduler block cell bursts can occur due to previously unused cell cycles. Each SB
has an event generator that determines when this SB should be served based on the
programmed SB rates. Because several SB may share one UTOPIA interface, it can
happen that events cannot be served immediately due to active cell transfers of previous
events. Such ’unused cell cycles’ are counted and can be used for later cell bursts
allowing a near 100% SB rate utilization. Cell bursts due to this mechanism are not rate
limited.
The maximum burst size (MBS) generated due to previously counted ’unused cell
cycles’, is controlled by bit field MaxBurstS(3:0) in the range 0..15 cells (a minimum value
of at least 1 is recommended). MaxBurst is programmed in registers
on Page
Per SB MBS dimensioning depends on the burst tolerance (BT) of subsequent devices
(buffer capacity and backpressure capability).
For example, if PHY(s) connected to the ABM-3G do not support backpressure and
provide a 3-cell transmit buffer, a value in the range 1..3 is recommended to avoid PHY
buffer overflows resulting in cell losses (e.g. typical for ADSL PHYs connected to the
ABM-3G).
If a PHY is connected that supports port specific backpressure to prevent its transmit
buffers from overflowing or provides sufficient buffering, the maximum value of 15 can
be programmed, guaranteeing a near 100% scheduler rate utilization.
Data Sheet
263.
CCR
SB
SB Rate Calculation Examples for SYSCLK = 51.84 MHz
SB
SB
SB
. The delivered CCR
=
measured at the scheduler output does not always match exactly
T
--------------------------------------------------------- -
32
SB
×
335.4037 335
á
T
SYSCLK
4.5878 4
1.1469 1
SB i á ñ
+
T
----------------
T
256
SB f á ñ
SB
SB(i)
is calculated by:
108
ñ
T
104
151
38
SB(f)
Operational Description
Delivered CCR
[cells/s]
PXF 4333 V1.1
“UECRI/DECRI”
1410612.245
352953.191
4829.963
2001-12-17
ABM-3G
o
SB
/
oo
(10)
and