Buffer Descriptors and Connection Tables
MPC885 PowerQUICC Family Reference Manual, Rev. 2
Freescale Semiconductor
37-5
0x00
(cont.)
4
L
Last in frame (AAL5). Set by the ATM controller when this buffer is the last in an AAL5
frame or when an error occurs, in which case one or more error bits are also set. The ATM
controller writes the total number of frame octets to the data length field.
0 The buffer is not the last in a frame.
1 The buffer is the last in a frame or an error has occurred.
5
F/OAM
F (AAL5) First in frame. Set by the ATM controller when this buffer is the first in a frame.
0 The buffer is not the first in a frame.
1 The buffer is the first in a frame.
OAM (AAL0) Operation and maintenance cell indication. Valid only in AAL0 buffers and
when an MCF filter is used. Used to recognize OAM cells within the ATM cell stream for
monitoring or alarm surveillance.
0 The current cell is not an OAM cell
1 The current cell is an OAM cell.
6
CM
Continuous mode.
0 Normal operation.
1 RxBD[E] is not cleared by the CPM after this BD is closed, allowing the associated
buffer to be overwritten next time the CPM accesses it.
7
FMC
Forward monitoring cell. Indicates the corresponding buffer has received an FMC cell to
which BRC fields have been added as described in
Section 39.3.2, “Terminating FMC
Cells.”
This flag is valid only for channels that activate performance monitoring (RCT[PM]
= 1).
0 Not an FMC cell
1 An FMC cell to which BRC fields have been added
8
HEC
HEC error (AAL5). A receiver HEC error occurred on at least one cell of the frame. Cells
with HEC errors are passed to the global raw cell queue with this bit set.
9
CLP
Cell loss priority. Indicates that at least one cell was received with its CLP bit set. This bit
is set in the last BD in the frame by the CP for channels that implement AAL5. For channels
that implement AAL0, this bit is copied from the CLP bit in the header of the received cell.
10
CNG
Congestion indication. Indicates that the last cell in the frame was received with its PTI
congestion bit set. This bit is set in the last BD of the frame by the CP for channels that
implement AAL5. For channels that implement AAL0, this bit is copied from the PTI bit in
the header of the received cell.
11
ABT
Abort (AAL5). Indicates that a frame abort was detected (last cell in frame indicated zero
frame length.) This error bit is set in the last BD of the aborted frame by the CP for
channels that implement AAL5.
12–13
—
Reserved, should be cleared during initialization.
14
LN
Receive length error (AAL5). Indicates the number of octets received in the frame does
not match the length specified in the length field of the AAL5 frame. This bit is set in the
last BD of the frame by the CP for channels that implement AAL5. Note that the whole
received PDU is written to the data buffer even if a receive length error is detected.
Table 37-1. ATM RxBD Field Descriptions (continued)
Offset from
RBD_PTR
Bits
Name
Description
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