![](http://datasheet.mmic.net.cn/380000/-PD98405_datasheet_16745025/-PD98405_165.png)
CHAPTER 5 SAR FUNCTION
165
Figure 5-29. Outline of Transmit Operation Flow
Y
Y
N
N
Y
Y
N
CRC-10
N
Fetches transmit descriptor
from system memory
Updates VC table
parameters
Schedules cells for
transmission
Reads VC table
parameters
Reads a segment from
system memory
Calculates and updates CRC-32
Updates packet length
Last buffer
Last cell
Transfers cell to PHY
layer
Calculates & inserts
CRC-10
Updates VC table with
next buffer descriptor
Adds AAL-5 trailer
Transmits indication write interrupt
occurrence in indication mailbox
(when the function is enabled)
Transfers cell to PHY
layer
AAL-5
AAL bit = 1
PTI
≠
"1xx"
5.4.6 Support of Non-AAL-5 Traffic
The
μ
PD98405 supports a function which does not add the AAL-5 trailer, instead transmitting raw cells to
enable the support of non-AAL-5 traffic. The
μ
PD98405 executes transmission as non-AAL-5 traffic when (1)
OAM F5 cell is transmitted and (2) raw cell is transmitted.
(1) OAM F5 cell transmission
When the host sets a pattern for the OAM F5 cells (PTI = 1xx) in the PTI field of the packet descriptor, the
μ
PD98405 does not add the AAL-5 trailer. When transmitting OAM F5 cells, the host sets one packet
descriptor per OAM F5 cell.
A CRC-10 operation can be inserted into OAM F5 cells. If the C10 bit of the packet descriptor is set to 1,
the
μ
PD98405 executes a CRC-10 operation on the 46 bytes and 6 bits of the 48 bytes of each OAM F5
cell segment, and overwrites the last 10 bits of the cell with the result, as a CRC-10 error detection code.
When enabling the CRC-10 operation insertion function, therefore, the host must set dummy data (all 0,
etc.) in the last 10 bits of the data buffer, so that the last 10 bits of the segment can be overwritten with an
error detection code.
When setting a packet descriptor for OAM F5 cell transmission, also note the following:
For OAM F5 cell transmission, the "AAL" bit must be set to 0.
Multi-buffer mode cannot be used. Always use single-buffer mode.
For OAM F5 cell transmission, set the size of the transmission buffer to 48 bytes, and set 48
bytes for the "SIZE" field of the packet descriptor.