Motorola PowerQUICC II MPC8280 Series Reference Manual page 1187

33.3.5.5 SSSAR Transmit Buffer Descriptor
The SSSAR buffer structure consists of a BD table that points to data buffers. The buffers
may contain SSSAR SDUs belonging to different CIDs. Each buffer may contain a whole
SSSAR SDU or part of it. The CPS CID is located in the first BD of the SSSAR SDU. See
Figure 33-12.
0 1
Offset + 0x00 R CM
Offset + 0x02
Offset + 0x04
Offset + 0x06
.
Table 33-5. SSSAR TxBD Field Descriptions
1
Offset Bits Name
0x00 0 R
1 CM
2 W
3 I
4 L
5-7 —
8-15 CID
MOTOROLA
Freescale Semiconductor, Inc.
2 3 4 5
W I L —
Data Length (DL)
Tx Data Buffer Pointer (TXDBPTR)
Figure 33-12. SSSAR TxBD
Ready
0 The buffer associated with this BD is not ready for transmission. The user is free to
manipulate this BD or its associated buffer. The CP clears R after the buffer is sent
or after an error condition is encountered.
1 The user-prepared buffer has not been sent or is currently being sent. No fields of
this BD may be written by the user once R is set.
Continuous mode
0 Normal operation.
1 The CP does not clear R after this BD is closed, allowing the associated buffer to
be retransmitted automatically when the CP next accesses this BD. However, the
R bit is cleared if an error occurs during transmission, regardless of the CM bit
setting.
Wrap (final BD in table)
0 This is not the last BD in the TxBD table.
1 This is the last BD in the TxBD table. After this buffer is used, the CP transmits
outgoing data for this channel from the first BD in the table (the BD pointed to by
the channel's TxBD_table_Base in the TxQD). The number of TxBDs in this table
is determined only by the W bit.
Interrupt
0 No interrupt is generated after this buffer has been serviced.
1 A Tx Buffer event is sent to the interrupt queue after this buffer is serviced. The
GHIN/GLIN bit in the event register is set when the INT_CNT counter reaches
terminal count.
Last.
0 This is not the last buffer of the SSSAR SDU.
1 This is the last buffer of the SSSAR SDU.
Reserved, should be cleared during initialization.
Contains the CID number of the SSSAR SDU pointed by this BD. This field should be
written to the first BD of an SSSAR SDU.
Chapter 33. ATM AAL2
For More Information On This Product,
Go to: www.freescale.com
7 8
CID
Description
AAL2 Transmitter
15
33-19