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CHAPTER 5 SAR FUNCTION
195
(d) CRC-32 error
Upon the completion of the transmission of all packet data to system memory, if the verification of the
CRC-32 result and the CRC-32 field in the received trailer produces a mismatch, notification of this
mismatch is posted.
A CRC-32 error is appended to the AAL-5 trailer, the last part of a packet to be received. Therefore,
the
μ
PD98405 does not detect an error until all of the packet data has been received and stored into
the receive buffer. Therefore, even if a packet causes a CRC error, all of the data for that packet will
be stored into the receive buffer.
If the AAL-5 trailer check reveals that a received packet contains both a CRC-32 error and Length
error, the posted error status will indicate the reception of a CRC-32 error.
(e) User abort
This error is reported if the "Length" field included in the receive trailer is found to be "0" when the field
is checked after all the packet data has been transferred to system memory. In this case, the received
packet is usually discarded as an invalid packet to the host.
(f)
"Length" error
Once all the data of a packet has been transferred to system memory, the
μ
PD98405 checks the
calculated packet length and the "Length" field included in the receive trailer. A "Length" error is
reported if either of the following conditions is satisfied:
("Number of receive cells x 48 bytes" - ""Length value" in trailer") > 55 bytes
("Number of receive cells x 48 bytes" - ""Length value" in trailer") < 8 bytes
(g) T1 timeout
A T1 error occurs if the last cell does not arrive within the T1R time, set by the user, of receiving the
first cell of the receive packet. The received data is retained in system memory until the T1R time
elapses. The start address and size of the packet are reported with a receive indication for reporting a
T1 timeout. The
μ
PD98405 discards all remaining cells, up to the last cell in this packet.
(h) Execution of Deactivate_Channel command
When the host issues a Deactivate_Channel command to the receive VC, the termination of command
processing is reported by the receive indication, regardless of whether a packet is currently being
received.
If the command is issued while the packet of the VC is being received, the cells stored in the receive
FIFO prior to the command being issued are transferred to system memory, and the start address and
size of the packet are reported by the same receive indication. While a packet is not being received, 0
is stored as the size in the receive indication.