Freescale Semiconductor MPC8260 - Manual (Page 997)

ATM Controller and AAL0, AAL1, and AAL5
MPC8260 PowerQUICC II Family Reference Manual, Rev. 2
Freescale Semiconductor 30-77
30.10.5.11 AAL1 TxBDs
Figure 30-51 shows the AAL1 TxBD.
Table 30-38. AAL5 TxBD Field Descriptions
Offset Bits Name Description
0x00 0 R 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.
1 — Reserved, should be cleared.
2 W Wrap (final BD in table)
0 Not the last BD in the TxBD table.
1 Last BD in the TxBD table. After this buffer is used, the CP sends outgoing data from
the first BD in the table (the BD pointed to by the channel’s TCT[TBD_BASE]). The
number of TxBDs in this table is determined only by the W bit. The current table cannot
exceed 64 Kbytes.
3 I 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.
FCCE[GINT x ] is set when the INT_CNT counter reaches the global interrupt
threshold.
4 L Last in frame. Set by the user to indicate the last buffer in a frame.
0 Buffer is not last in a frame.
1 Buffer is last in a frame.
5 — Reserved, should be cleared.
6 CM 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 CM.
7-9 — Reserved, should be cleared.
10 CLP The ATM cell header CLP bit of the cells associated with the current frame are ORed with
this field. This field is valid only in the first BD of the frame.
11 CNG The ATM cell header CNG bit of the cells associated with the current frame are ORed
with this field. This field is valid only in the first BD of the frame.
12–15 — Reserved, should be cleared.
0x02 — DL The number of octets the ATM controller should transmit from this BD’s buffer. It is not
modified by the CP. The value of DL should be greater than zero.
0x04 — TXDBPTR Tx data buffer pointer. Points to the address of the associated buffer, which may or may
not be 8-byte-aligned. The buffer may reside in either internal or external memory. This
value is not modified by the CP.