MSC8144E Reference Manual, Rev. 3
18-6
Freescale
Semiconductor
QUICC Engine™ Subsystem
RxBD data length. The number of bytes the RISC processor writes into the RxBD buffer
once the BD closes. The RISC processor updates this field after the received data is placed
into the buffer and the buffer is closed. You do not need to initialize this field. In
frame-based protocols,
RxBD.bd_length
contains the total frame length including CRC
bytes. If a received frame length, including CRC, is an exact multiple of the parameter
RAM maximum receive buffer length MRBLR, the last buffer holds no actual data but the
associated BD contains the total frame length.
TxBD data length.
T
he number of data bytes the controller needs to transmit from its
buffer. The RISC processor never modifies this field. This field needs to be initialized by
the user.
Buffer pointer. The 32-bit data at
0x4
, which points to the beginning of the
buffer in internal or external memory.
RxBD buffer pointer. The buffer pointer value must be a multiple of four to be
word-aligned.
TxBD buffer pointer. The buffer pointer value can be even or odd
.
18.2.5
Multithreading
The Ethernet Controllers are able to processes frames or cells at high bit rates (gigabit Ethernet
and above OC-3 nominal rates). In order to achieve these bit rates the UCC receiver and the UCC
transmitter are able to process multiple frames/cells simultaneously at any given time. This is
implemented with the multithreading mechanism. Each thread processes a different frame/cell.
The multithreading processing mechanism comprises three components: Distributor, Threads and
in some cases Terminator. Figure 18-3 shows a high-level diagram of the multithreading
architecture.
Each one of the components (distributor, threads and terminator) has an ID number associated
with it, referred to as its Serial Number (SNUM). The distributor SNUM is always the SNUM of
the UCC receiving or transmitting the data. Each one of the transmitter and receiver threads has
its own parameter RAM located in the multi-port RAM. The user software initializes the values
for the SNUM and the pointer of the parameter RAM base address at initialization time.
Note:
See the QUICC Engine™ Block Reference Manual with Protocol Interworking
(QEIWRM).for specific interface configuration details.
Figure 18-3. Multi-Threading Processing Mechanism
Distributor
Thread1
Thread2
Thread3
Terminator
Содержание MSC8144E
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