NEC Network Controller uPD98502 User Manual
CHAPTER 4 ATM CELL PROCESSOR
Preliminary User’s Manual S15543EJ1V0UM
275
(2) Max No. of bytes violation
This error occurs if the last cell of a packet has not been received when the number of cells received has reached
the user-specified "Max. No. of bytes" When the next cell is received, the RID bit is set and a receive indication is
issued. The subsequent cells of the packet, including the last cell, are discarded.
(3) CRC-32 error
This error occurs if the CRC-32 value does not match the CRC-32 value contained in the receive trailer when all of
cell data in the packet has been received. If a check made on the trailer reveals that the received packet has both
CRC-32 and "length" errors, the CRC-32 error is reported as the error status in the receive indication.
(4) "length" error
This error is reported if the "length" field contained in the receive trailer and the calculated packet length satisfy
either of the following conditions:
("Number of received cells x 48 bytes" – ""length" value in the trailer") > 55 bytes
("Number of received cells x 48 bytes" – ""length" value in the trailer") < 8 bytes
(5) T1 time-out
This error occurs if the last cell of a packet has not been received even after the user-specified A_T1R time has
elapsed since the first cell was received. When this error occurs, the RID bit is set and the remaining cells of the
packet that caused this error, including the last cell, are discarded.
The table below lists the errors that can occur with any of the first cell, the immediate cells, and the last cell of a
packet.
Table 4-4. Reception Errors That Can Occur During Packet Reception
Error
When a cell is discarded
When a receive indication is issued
Handling of other cells
after the error occurred
Free buffer
underflow
The cell received when the size of
the free buffer is insufficient is
discarded.
Time at which transfer becomes
impossible during segment transfer
The subsequent cells of the packet,
including the last cell, are
discarded.
MAX No. of
Segments
error
The cell received after MAX No. of
Segments was reached is
discarded.
Time at which the next cell is
received after MAX No. of
Segments was reached
The subsequent cells of the packet,
including the last cell, are
discarded.
T1 error
The cell received after the T1 time
has elapsed is discarded.
Time at which T1 time has elapsed.
The subsequent cells of the packet,
including the last cell, are
discarded.
Two or more errors may occur at the same time; however, only one is reported with a receive indication. The table
below lists the error reporting priorities.
Table 4-5. Error Reporting Priorities
Underflow
MAX error
CRC error
Length
T1 error
Underflow
-
Underflow
Underflow
Underflow
Underflow
MAX error
-
-
MAX error
MAX error
MAX error
CRC error
-
-
-
CRC error
CRC error
Length
-
-
-
-
Length
T1 error
-
-
-
-
-