PM7311 pmc-sierra, PM7311 Datasheet - Page 65

• Manufacturer Part Number: PM7311
• Description: Freedm 84a1024l Assp Telecom Standard Datasheet
• Manufacturer: pmc-sierra

Proprietary and Confidential to PMC-Sierra, Inc., and for its customers’ internal use.
Document No.: PMC-2021832, Issue 2
Figure 15 Egress Data Flow
Full packets must be transferred from the upstream device to the FREEDM 84A1024L via the
Any-PHY interface . When supporting a multi-link bundle, the Any-PHY channel is mapped to
multiple HDLC channels. The transmit fragmentor will fragment packets/frames and distribute
the fragments across all the HDLC channels in the multi-link bundle applying the appropriate
sequence number to each of the fragments. The fragmentation size is programmable on a per
connection basis. The fragmentation size is referenced to the number of bytes transferred on the
link and includes the multi-link header.
On an HDLC channel and priority basis the datagrams are decomposed into chunks and are stored
in an external SDRAM memory. A chunk is defined as a fixed length unit of data (32 bytes) plus a
4 byte header, or a partially completed unit of data. A chunk will only consist of data from one
packet/frame.
The Egress Queue Manager maintains a separate linked list of chunks for each HDLC channel
and priority level. Single link HDLC channels have two priority levels whereas HDLC channels,
which are part of multi-link bundles, have only one priority level.
The chunk transmitter controls a 64 Kbyte partial packet RAM. A data chunk is transferred from
external memory into the partial packet RAM in a burst. Data is read from the RAM a byte at a
time and delivered to the HDLC engine. The chunk transmitter can support 1024 simultaneous
byte transfer sessions (one per HDLC channel). As chunks are depleted, the chunk transmitter
requests the next chunk for the associated HDLC channel from the egress queue manager. The
egress queue manager will read a chunk from the appropriate link list, giving preference to high
priority data over low priority data.
The HDLC engine receives the incoming byte stream and encapsulates the data stream with a
HDLC header, bit stuffing and a FCS trailer. The HDLC engine is capable of simultaneously
processing 1024 independent HDLC channels. The resulting HDLC data and status is passed to
the de-channelizer to be transferred onto the links.
Bitstreams per link
INSBI336
Bytes per HDLC Channel
Channel-
De-
izer
Block per HDLC Channel
FREEDM 84A1024L ASSP Telecom Standard Product Data Sheet
HDLC
Partial
Packet
Processor
Egress
Queue
Manager
TFRAG Builder
ANY
PHY
I/F
Released
65