RELEASED
PM73123 AAL1GATOR-8
DATASHEET
PMC-2000097
ISSUE 2
8 LINK CES/DBCES AAL1 SAR
Figure 49 Pointer/Structure State Machine
No pointer
found
Underrun
Non-dummy
pointer found and
parity good (or not
Underrun or
force-underrun
Pointer does not
match prediction or
underrun or
checking parity)
force-underrun (or
checking parity and
Pointer Found
Underrun or
force-underrun
Structure
found
Pointer does not
match prediction
(or parity bad and
checking parity) or
out-of-sequence or
invalid cell
Pointer matches
prediction and
parity good (or not
Structure Found
checking parity)
One Mismatch
(Signaling is
not updated)
Pointer matches prediction
and parity good (or not
checking parity)
9.2.2.2.9 Overrun
Overrun occurs when the data in the buffer is removed at a slower rate than it is
filled. However, because the AAL1gator-8 buffers are quite large, 16 Kbytes per
line, by the time this happens, all data in the buffer can be quite old. Therefore,
the buffer size is adjustable, which regulates how much data can be stored in the
buffer before an overrun occurs. The R_MAX_BUF field in the R_BUF_CFG
register controls the maximum size of the receive buffer. The value of
R_MAX_BUF should be equal to or greater than two times CDVT, or CDVT plus
two times the number of frames required per cell, whichever is greater. If
MF_ALIGN is set, then extra margin should be added for the additional multi-
frame of data that may be present. Therefore the value should be increased by
16 frames for E1 or 24 frames for T1.
The amount of data that is buffered during DBCES mode is different than the
amount of data that is buffered in normal mode. In DBCES mode there must be
enough data to handle the case where the structure changes from the maximum
number of channels being active to only one channel being active without going
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