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CHAPTER 4 ATM CELL PROCESSOR
Preliminary User’s Manual S14767EJ1V0UM00
329
Figure 4-44. Receive Indication Format
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UINFO
PACKET SIZE
TIME STAMP
PACKET
ADDRESS
CHANNEL NUMBER
ERR
:Pattern set by the host in the UINFO field in the VC table
:Size of the receive packet in cell units
:Value of A_TSR when this indication is issued
:Start address of the batch used
START
:VC NUMBER used by this VC
:If 1, indicates that an error occurred while the packet was being received.
If 0, indicates that the packet was received normally.
:The PTI field in the header of at least one cell of the packet indicated congestion.
:The CLP field in the header of at least one cell of the packet was equal to 1.
:Status of the error that occurred
0000
No error
0001
Free buffer underflow
0011
MAX NUMBER OF SEGMENT violation
0100
CRC-32 error
0101
User abort
0110
Length error
0111
T1 time-out
:Number of the pool used
CI
CLP
ERROR STATUS
POOL NUMBER
4.8.3.4 Receive errors
ATM Cell Processor checks for receiving errors while a packet is being received and using trailer information when
the packet has been received. Upon detecting an error, it reports the type of error and the start address and the
amount of data that had been transferred to SDRAM prior to the error being detected, using the receive indication to
be stored in the mailbox.
Upon receiving a receive indication containing the error status, the host takes appropriate action and discards the
packet that caused the error. The types of reception errors are described below:
(1) Free buffer underflow
This error occurs if the free area in the free buffer in SDRAM is 48 bytes or less when a packet is received. When
this error occurs, an A_RQU interrupt is generated. If the discarded cell is an intermediate cell or the last cell of the
packet, reception of the packet is suspended, a receive indication reporting the free buffer underflow error is issued,
and the RID bit in the VC table is set. The remaining cells of the packet, including the last cell, are discarded, and the
RID bit is referenced. When the last cell is received, the RID bit is reset. If the cell discarded due to this error is the
first cell of the packet, an A_RQU interrupt is generated and the RID bit is set. No receive indication is issued,
however.