pxf4333 Infineon Technologies Corporation, pxf4333 Datasheet - Page 106

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

4.2.2
4.2.2.1
The aggregate theoretical peak cell rate of the SBS is calculated as follows:
SYSCLK designates the core clock frequency. Each cell cycle needs 32 clock cycles.
With the core SYSCLK = 51.84 [MHz] we have PCR
This corresponds to 686,8 [Mbit/s] for 53 byte cells
Note: Due to the need to perform internal SDRAM refresh cycles, the PCR
4.2.2.2
For the peak cell rate of an SB we can have PCR
In the following, let LC denote the logical channel assigned to an SB. Recall that a logical
channel can subsume the whole output port or an reasonable subdivision.
Let CCR
CCR
possible. Both permanent overload, leading to UTOPIA backpressure, and permanent
underload, leading to poor channel utilization, should be avoided.
Overall, the following holds
Note: For short periods of time PCR
Deriving Internal Parameters from a Given CCR
Internally the scheduler block output cell rate CCR
T
T
These parameters are dimensionless and thus only indirectly represent the output rate.
The following formulas show how to derive the two parameters assuming a given desired
output rate CCR
Data Sheet
SB(i)
SB(f)
SB(LC)
[13:0], the 14 bit integer division factor
[7:0], the 8 bit fractional division factor
empty cells. A discussion on the empty cell rate PCR
maximum scheduler block rate is contained in
independent of the particular CCR
SB
= PCR
denote the configured cell rate of an SB (i.e. the desired output cell rate).
Programming Queue Scheduler Rates and Granularities
Scheduler Block Scheduler
Programming the Scheduler Block Rates
PCR
å
LC
CCR
SB
SBS
LC
:
SB(LC)
must be chosen to match the peak cell rates of the LC as close as
=
SYSCLK
---------------------- -
≤
32
PCR
UTOPIA
[
cells s ⁄
SB
SB
106
as defined above can occur internally,
]
SB
SB
SB
SBS
Section
= PCR
is represented by two parameters:
= 1620000 [cells/s].
SBS
Operational Description
4.2.2.4.
empty
- PCR
, which restricts the
empty
PXF 4333 V1.1
.
SBS
2001-12-17
ABM-3G
contains
(3)
(4)