RELEASED
PM73123 AAL1GATOR-8
DATASHEET
PMC-2000097
ISSUE 2
8 LINK CES/DBCES AAL1 SAR
While in the OUT_OF_SYNC state, if another cell is received with a valid SN and
in the correct sequence, then the SYNC state is entered and the cell is accepted.
Otherwise, if a cell with an invalid SN is received, then the START state is re-
entered and the cell is dropped. Otherwise, if the cell has a valid SN but is in the
incorrect sequence, then the cell is dropped and the RALP remains in the
OUT_OF_SYNC state.
While in the SYNC state, if another cell is received with a valid and correct SN,
the RALP remains in the SYNC state. Otherwise, if an invalid SN is received, the
RALP goes to the INVALID state; or if a valid but incorrect SN is received, the
OUT_OF_SEQUENCE state is entered. All cells received while in the SYNC
state are accepted.
While in the INVALID state, four possibilities can occur.
1. If the cell received has an invalid SN, the START state is re-entered and the
cell is dropped.
2. If the cell received has a valid SN and is in sequence with the last valid SN,
then a misinserted cell is detected and RALP returns to the SYNC state, but
the cell is dropped to keep SN integrity because the previous cell has already
been sent.
3. If the cell received has a valid SN and is equal to SN + 2 with respect to the
last valid SN, then the RALP returns to the SYNC state and the cell is
accepted.
4. Otherwise, if the SN is valid but does not meet any of the previous criteria,
then the cell is dropped and the OUT_OF_SYNC state is entered.
While in the OUT_OF_SEQUENCE state, five possibilities can occur.
1. If the cell received has an invalid SN, the START state is re-entered and the
cell is dropped.
2. If the SN is valid and in sequence with the last valid, in sequence SN, then a
misinserted cell is detected and RALP returns to the SYNC state, but the cell
is dropped to keep SN integrity because the previous cell has already been
sent.
3. If the SN is valid and the SN is in sequence with the SN of the previous cell,
the RALP assumes cells were lost; it inserts a number of dummy cells
identical to the number of lost cells, accepts the cell and returns to SYNC. If
the number of lost cells is greater than MAX_INSERT, then no cells are
inserted and a forced underrun occurs. If an underrun occurred when cells
were lost, no cells are inserted unless bit integrity through underrun is
PMC-SIERRA, INC. PROPRIETARY AND CONFIDENTIAL
108
PMC [ PMC-SIERRA, INC ]
