PXF4336 Datasheet, PDF (68/425 Pages) Infineon Technologies AG – ABM Premium ATM Buf fer Manager

ABM-P
PXF 4336 V1.1
Functional Description
3.4.1.3 Threshold Classification
The different threshold types are listed in Table 3-17. In this section, each classification
includes a short description.
3.4.1.3.1 Discard Thresholds
Discard thresholds are used by the Cell Acceptance Algorithm (see Chapter 3.4.1.7).
The CAA is invoked every time a cell arrives and calculates a truth value from individual
discard conditions.
A discard condition is an expression involving thresholds, counters, flags, parameters,
and state variables that renders a truth value as result. Several basic discard conditions
can be combined to implement more advanced discard mechanisms (see
Chapter 3.4.1.6).
Basic Discard Conditions
The simplest discard condition is the comparison of an occupancy counter with a
threshold. A common classification of discard conditions includes:
• Maximum
A discard condition is classified as Maximum Fill if it is independent of the CLP
transparency flag or if the CLP transparency flag is set to 1.
• CLP1
A discard condition is classified as CLP1 if it is dependent on the setting of the CLP
transparency flag to 0.
• Packet
A discard condition refers to a packet if it is dependent on the setting of EPDen = 1 or
PPDen = 1.
A particular threshold can participate in several discard conditions. In the ABM-P, it is
quite common to use a threshold in both maximum fill and packet discard conditions.
Refer to Table 3-17.
Discard Control Parameters
Besides the simple comparison of a threshold value to a counter, several flags and
variables are combined to provide more complex discard conditions.
• CLP1DIS
CLP1 thresholds are only enabled if the number of CLP1 cells in the SB, counted by
SBOccLP is greater or equal to CLP1DIS. To enable CLP1 thresholds unconditionally,
this threshold must be set to 0 in Register 19 "CLP1DIS" on Page 218.
• MinBG
This queue-specific threshold disables discard when the QueueLength counter is
lower than MinBG. The description of the minimum buffer guarantee in
Section 3.4.1.6.4 provides the details.
Data Sheet
68
2001-12-17