RELEASED
PM73123 AAL1GATOR-8
DATASHEET
PMC-2000097
ISSUE 2
8 LINK CES/DBCES AAL1 SAR
• The structure used for signaling is determined by the mode of the line and the
value of E1_WITH_T1_SIG in the LIN_STR_MODE register. Normally the
signaling structure will follow the mode of the line. However if the line is in E1
mode and E1_WITH_T1_SIG is set, then a T1 signaling structure is used.
This means that for a single DS0, signaling is updated after 24 data bytes
instead of after 16 data bytes.
• If the line is in SDF-MF mode and R_CHAN_NO_SIG = 1 in the R_BUF_CFG
word, then the queue is handled as if it is in SDF-FR mode. The structure
should be adjusted from a multiframe structure to a frame structure. For
example, a channel with two DS0s would have a structure size of two bytes
when R_CHAN_NO_SIG is set and a structure size of 49 bytes (include two
signaling nibbles) if in T1 mode when R_CHAN_NO_SIG is off.
9.2.2.2.7 Underrun
The AAL1gator-8 declares an underrun condition for a VC when no data is
present in the VC receive buffer. When this situation occurs, the AAL1gator-8
plays out conditioned data and frozen signaling onto the timeslots assigned to
the VC experiencing underrun. Timeslots generated by other VCs are unaffected.
Each time a cell is received after a queue has entered an underrun condition, the
UNDERRUN sticky bit is set. RALP does not know about an underrun until a cell
is received for the queue that underflowed. To make sure that each underrun is
counted only once, RALP will increment the R_UNDERRUN counter when
exiting the underrun state and entering the resume state. The initial underrun
caused by reset is not counted. Forced underruns due to other errors are not
counted by the underrun counter.
Each time a queue enters or exits the Underrun state an entry will be made to
the RCV_STAT_FIFO.
If the underrun counter is read and the queue is currently in underrun, the
present underrun condition will not be accounted for until the queue exits
underrun. To determine if the queue is in underrun, check the value of the
R_UNDERRUN bit in the R_LINE_STATE register. When not in UDF-HS mode,
the choice of conditioning data while in underrun depends on the value of
RX_COND in the R_CH_QUEUE_TBL. Three choices for data exist:
1. Play out the data from R_COND_DATA (Default).
2. Play out pseudorandom data . (For applications that are sensitive to constant
data.) The pseudorandom data option uses the data from R_COND_DATA
and then replaces the most significant bit with the result of an 18th order
polynomial, specifically x18 + x7 + 1.
PMC-SIERRA, INC. PROPRIETARY AND CONFIDENTIAL
123
PMC [ PMC-SIERRA, INC ]
