User manual

ATM AAL2
MPC8260 PowerQUICC II Family Reference Manual, Rev. 2
Freescale Semiconductor 32-33
32.4.4.8 SSSAR Receive Buffer Descriptor
The SSSAR SDU is stored in a BD-buffer structure similar to the structures used for AAL5 frames. The
buffer size is determined by SSSAR RxQD[MRBLR]; the actual buffer space used may be smaller. If the
received SSSAR SDU is greater than MRBLR, the SDU spans over multiple buffers.
The SSSAR RxBD is shown in Figure 32-21.
Table 32-12 describes the SSSAR RxBD fields.
0x02 — RxBD Table
Offset
Points to the next BD to be handled by the CP. The user should initialize this pointer to
zero.
0x04 — RxBD Table
Base
Points to the beginning of the BD table.
0x08 — — Reserved, should be cleared during initialization.
0x0A — — Reserved, should be cleared during initialization.
0x0C — Time Stamp Used for reassembly timeout of the SSSAR SDU. Whenever the first packet of an
SSSAR SDU arrives the timestamp timer is sampled and stored here (regardless of
the RasT bit).
0x10 — — Reserved, should be cleared during initialization.
0x12 — — Reserved, should be cleared during initialization.
0x14 — MRBLR Maximum receive buffer length. Holds the maximum receive buffer length. The actual
buffer size can be less.
0x16 — Max_SSSAR
_SDU_
Length
Holds the maximum SSSAR SDU length. Upon each new packet the accumulated
frame size is compared with this value. If the limit is exceeded, the CP discards the rest
of the packets of the current frame.
0x18–
0x1E
— — Reserved, should be cleared during initialization.
1
Boldfaced entries must be initialized by the user.
01234567 1011 15
Offset + 0x00 ECMW I L RxError — UUI
Offset + 0x02 Data Length (DL)
Offset + 0x04 Rx Data Buffer Pointer (RXDBPTR)
Offset + 0x06
Figure 32-21. SSSAR Receive Buffer Descriptor
Table 32-11. SSSAR RxQD Field Descriptions (continued)
Offset Bits Name
1
Description