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IXP400 Software
Access-Layer Components: HSS-Access (IxHssAcc) API
April 2005 IXP400 Software Version 2.0 Programmer’s Guide
214 Document Number: 252539, Revision: 007
13.7.2 Data Flow in Channelized Service
Data in the time slots configured as Voice64K/Voice56K types will be provided to the client via the
IxHssAcc channelized service. There are up to 32 such channels per HSS port. The channelized
service uses memory that is shared between the Intel XScale core and the NPEs. The client is
responsible for allocating the memory for IxHssAcc to transmit and receive data through the HSS
port.
For receive,
ixOsServCacheDmaAlloc() of the IxOSCacheMMU component can be used to create a
pointer to a pool of contiguous memory from the shared memory of the Intel XScale core and the
NPEs. The pointer to this Rx data pool needs to be a physical address because NPE will directly
write data into this memory area. The memory pool is divided into N circular buffers, one buffer
per channel. N is the total number of channels in service.
Figure 68. HSS Packetized Transmit Buffering
NPE-A
Hss Packetized Tx
Operation
2. Data (HDLC frame or RAW block)
for each packet-pipe read
from appropriate mbuf, specified
by descriptor
3. HDLC frame processing
performed on each
packet-pipe configured
for HDLC mode
HssPacketizedTx0 -
HssPacketizedTx3
queues
1. Descriptor read
from packet-
pipe-specific,
Tx queue
IXP_BUFs
4. Data transmitted
to HSS port
HssPacketizedTxDone
queue
5. Descriptor returned
when entire frame/
block sent.
F0-
TSa
F0-
TSb
F0-
TSc
...
F0-
TSz
Frame 0
F1-
TSa
F1-
TSb
F1-
TSc
...
F1-
TSz
Frame 1
...
HSS Port Serial Data Stream
(TSa, TSb, ... = timeslots configured as "HDLC")
B2383-03