Motorola PowerQUICC II MPC8280 Series Reference Manual page 1092

ATM Memory Structure
Table 31-37 describes AAL0 RxBD fields.
Offset Bits Name
0x00 0 E
1 —
2 W
3 I
4–5 —
6 CM
7–9 —
10 CRE
11 OAM
12-15 —
0x02 — DL/CC
0x04 — RXDBPTR Rx data buffer pointer. Points to the first location of the associated buffer; may reside in
31.10.5.7 AAL1 CES RxBD
Refer to Section 32.12.1, "AAL1 CES RxBD."
31.10.5.8 AAL2 RxBD
Refer to Section 33.4.4.4, "CPS Receive Buffer Descriptor (RxBD)."
31-78
Freescale Semiconductor, Inc.
Table 31-37. AAL0 RxBD Field Descriptions
Empty
0 The buffer associated with this RxBD is filled with received data, or data reception was
aborted due to an error. The core can examine or write to any fields of this RxBD. The
CP does not use this BD again while E remains zero.
1 The Rx buffer is empty or reception is in progress. This RxBD and its associated
receive buffer are owned by the CP. Once E is set, the core should not write any fields
of this RxBD.
Reserved, should be cleared.
Wrap (final BD in table)
0 This is not the last BD in the RxBD table of the current channel.
1 This is the last BD in the RxBD table of the current channel. After this buffer has been
used, the CP will receive incoming data into the first BD in the table. The number of
RxBDs in this table is programmable and is determined only by the W bit. The current
table cannot exceed 64 Kbytes.
Interrupt
0 No interrupt is generated after this buffer has been used.
1 An Rx buffer event is sent to the interrupt queue after the ATM controller uses this
buffer. FCCE[GINTx] is set when the INT_CNT reaches the global interrupt threshold.
Reserved, should be cleared.
Continuous mode
0 Normal operation.
1 The CP does not clear the E bit after this BD is closed, allowing the associated buffer
to be overwritten automatically when the CP next accesses this BD.
Reserved, should be cleared.
Rx CRC error. Indicates a CRC10 error in the current AAL0 buffer. The CRE bit is
considered an error only if the received cell had a CRC10 field in the cell payload.
Operation and maintenance cell. If OAM is set, the current AAL0 buffer contains an OAM
cell. This cell is associated with the channel indicated by the channel code field (CC field).
Reserved, should be cleared.
Data length/channel code. If RxBD[OAM] is set, this field functions as CC; otherwise, it is
DL. Data length is the size in octets of this buffer (MRBLR value). Channel code specifies
the channel code associated with this OAM cell.
either internal or external memory. This pointer must be burst-aligned.
MPC8280 PowerQUICC II Family Reference Manual
For More Information On This Product,
Go to: www.freescale.com
Description
MOTOROLA