Motorola PowerQUICC II MPC8280 Series Reference Manual page 1184

AAL2 Transmitter
Figure 33-9 shows a CPS TxBD.
0 1
Offset + 0x00 R CM
Offset + 0x02
Offset + 0x04
Offset + 0x06
Table 33-3 describes the CPS TxBD fields.
.
Offset Bits Name
0x00 0 R
2
1 CM
2 W
3 I
4-7 —
8-15 CPS Packet
Header
0x02 — CPS Packet
Header
0x04 — TXDBPTR
1
Boldfaced entries must be initialized by the user.
2
Setting Continuous mode (TxBD[CM] = 1) is not allowed in CID switching mode.
33-16
Freescale Semiconductor, Inc.
2 3 4
W I —
Tx Data Buffer Pointer (TXDBPTR)
Figure 33-9. CPS TxBD
Table 33-3. CPS TxBD Field Descriptions
1
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.
Reserved, should be cleared during initialization.
This field contains the beginning (MSB) of the 3-byte packet header. See
Figure 33-10 for the CPS packet header format.
This field contains the rest of the packet header. If TxQD[HEC] = 0, the HEC part of
the packet header is calculated by the CP, and the user may disregard the five
least-significant bits of this field. See Figure 33-10 for the CPS packet header format.
Tx data buffer pointer. Points to the address of the associated buffer. There are no
byte-alignment requirements for the buffer, and it may reside in either internal or
external memory. This pointer is not modified by the CP.
MPC8280 PowerQUICC II Family Reference Manual
For More Information On This Product,
Go to: www.freescale.com
7 8
CPS Packet Header
CPS Packet Header
Description
15
MOTOROLA