Datasheet

____________________________________________________ DS34S101, DS34S102, DS34S104, DS34S108
Rev: 032609 67 of 198
Figure 10-49. TDM-over-Packet Data Flow Diagram
10.6.11.1 Buffer Descriptor
Data is transferred between the Ethernet MAC, internal payload-type machines and the external CPU by means of
buffers in the SDRAM. Payload data is stored in 2 kB SDRAM buffers along with a buffer descriptor located in the
buffer’s first dwords. The buffer pointers are managed inside the TDMoP block and are stored in queues, pools,
and other internal blocks. Queues store pointers to SDRAM buffers containing packet data to be processed, while
pools store pointers to empty buffers. The pointers are passed from one block to another. Only the block owning
the pointer can access the associated buffer.
The size of the buffer descriptor size depends on the internal path it is used for:
TDM  TDM, TDM  CPU and CPU  TDM: One dword
TDM  ETH, CPU  ETH and ETH  TDM: Two dwords
ETH  CPU: Three dwords
The fields of the buffer descriptor dwords are described in the sections below.
HDLC
PAYLOAD
TYPE
MACHINE
AAL1
PAYLOAD
TYPE
MACHINE
TDM
TO
CPU
QUE UE
FREE
BUFFER
POOL
ETH
TX
QUE UE
TDM
TO
CPU
POOL
TX
ETH
INTERFACE
CPU
TO
ETH
QUE UE
CPU
TX
RETURN
QUE UE
ETH
TO
CPU
QUE UE
CPU
TO
TDM
QUE UE
CPU
RX
RETURN
QUE UE
ETH
TO
CPU
POOL
CROSS
-
CONNECT
QUE UE
ETH
MAC
PACKET
CLASSIFIER
RX
FIFO
SDRAM
RX
ARBITER
RAW
PAYLOAD
TYPE
MACHINE