PXF4333 Datasheet, PDF (87/361 Pages) Infineon Technologies AG – ABM 3G ATM Buf fer Manager

ABM-3G
PXF 4333 V1.1
Functional Description
Optionally, the ATM cell header may be overwritten with a new value programmed in the
MGT by setting ’LCIOen’ = 1 and ’LCI’ to the desired value in Register 51 "MGT2" on
Page 234.
A queue is released from its VC-merge group by setting ‘QIDvalid’ = 0 in Register 38
"QCT1" on Page 214.
It is recommended to set the parameters of the individual queues in a merge group to
equal values, reflecting the desired properties of the outgoing merged VC. In particular,
the user must make sure that all queues of a merge group are assigned to the same SB.
Also, for the optional shaping of a merged VC, the shaping parameters TP, TS, tauS and
Config must be specified for each of the logical queues of the merge group and should
all be equal to the intended shaping parameters of the outgoing merged VC.
The VC-merge shaping mechanism works round robin on a per queue basis with the
changing of the QID going on transparently behind the scene. Hence, viewed from the
outgoing VC, there is no difference between a single queue VBR shaping and a merge
queue VBR shaping. In particular, no cell slot is lost on the transition between queues.
3.4.2.5.2 Dummy Queue
A ‘dummy queue’ (in contrast to a normal queue) is always scheduled by the queue
scheduler according to its associated rates and parameters, even though it does not
contain stored cells. Scheduling a dummy queue results in an ’empty cell cycle’ (no cell
is emitted during this cycle).
Storing cells into a dummy queue is possible, but not recommended, since the cells are
never emitted.
Dummy queues can be used for bandwidth reservation e.g. for subsequent multicast
operation or any other cell insert/multiplier process.
A queue can be configured as a ‘dummy queue’ by setting ’DQac = 1’ and ‘RSall’ = 1 in
Register 38 "QCT1" on Page 214. This may only be done if ’MGconf/DQsch’ = 0 in
Register 39 "QCT2" on Page 217 and the queue is empty (QueueLength = 0).
Data Sheet
87
2001-12-17