Freescale Semiconductor MPC8260 - Manual (Page 1055)

ATM AAL1 Circuit Emulation Service
MPC8260 PowerQUICC II Family Reference Manual, Rev. 2
Freescale Semiconductor 31-39
Table 31-11 describes AAL1 CES RxBD fields.
0 1 2 3 4 5 6 7 8 9 10 11 15
Offset + 0x00 E — W I — — CM — — EOSF —
Offset + 0x02 Data Length
Offset + 0x06 Rx Data Buffer Pointer
Offset + 0x08
Figure 31-28. AAL1 CES RxBD
Table 31-11. AAL1 CES RxBD Field Descriptions
Offset Bits Name Description
0x00 0 E 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 read or write any fields of this RxBD. The CP
cannot use this BD again while E = 0.
1 The buffer is not full. 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.
1 — —
2 W 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 this current channel. After this buffer is used, the
CP receives 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 overall
space is constrained to 64 Kbytes.
3 I 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[GINT x ] is set when the INT_CNT reaches the global interrupt threshold.
4-5 — —
6 CM • Continuous mode
0 Normal operation.
1 The empty bit (RxBD[E]) is not cleared by the CP after this BD is closed, allowing the
associated buffer to be overwritten automatically when the CP next accesses this BD.
7-8 — —
9 EOSF End of super frame. CES mode (RCT[CESM=1]) only.
0 No signaling information should be inserted after closing this buffer.
1 When closing this buffer, the ATM receiver unpacks the CAS information from the
incoming AAL1 cells and stores it in the internal CAS block.
Note that this bit should be set by the user at the end of each super-frame in the common
(MCC, ATM) BD table. See Section 31.4.6, “Channel Associated Signaling (CAS)
Support .”
10-15 — —
0x02 — DL Data length. The number of octets the CP writes into the buffer once its BD is closed.
0x04 — RXDBPTR Rx data buffer pointer. Points to the first location of the associated buffer; may reside in
either internal or external memory. This pointer must be burst-aligned.