PXF4336 Datasheet, PDF (91/425 Pages) Infineon Technologies AG – ABM Premium ATM Buf fer Manager

ABM-P
PXF 4336 V1.1
Functional Description
3.4.2.5 VC-Merge and Dummy Queue
Any queue can be configured (mutually exclusive) to participate in a VC-merge group or
as a ‘dummy queue’. A detailed description of enabling/disabling those special queue
functions is provided in the description of “Queue Configuration Table Transfer
Registers QCT0..6” on Page 258.
3.4.2.5.1 VC-Merge
Several logical queues carrying AAL5 packets may be grouped together into one of a
maximum of 128 merge groups. Functionally, a Packet Round-Robin (PRR) scheduler
stage is inserted between the queues of the merge group and the first scheduling stage
of the scheduler block. Whenever a complete packet is queued in a QID of a merge
group, this QID is enabled to the PRR. The PRR schedules a QID to the SB until all cells
of the current packet are transmitted. Then it switches to the next enabled QID.
Hence, viewed from the Scheduler Block, a merge group appears like a single queue
with the additional benefit that the output VC maintains AAL5 packet boundaries. See
Figure 3-31.
Packet a
VCx
Packet b
VCy
Merge
Group
QIDx
Active QIDx
QIDy
Output with VC merge function
Packet b Packet c
Packet a
VC
Packet c
VCz
ATM cell
optional shaper
QIDz
Packet-RR SB
Output without VC merge function
Packets destroyed
Figure 3-31 VC Merge Scheduling
Any queue can be configured to be member of one of the 128 merge groups in the QCT
by setting ’RSall’ = 0 in Register 44 "QCT1" on Page 261 and then setting ’MGconf/
DQsch’ = 1 and ’MGID’ to the desired merge group identifier in Register 45 "QCT2" on
Page 264.
If the queue is the first queue of the merge group, then its QID must be written into field
’Head_Pointer’ in Register 57 "MGT2" on Page 281.
Assigning a queue to a VC-merge group already enables the packet boundary aware
scheduling of all queues within the same group.
Data Sheet
91
2001-12-17