MPC8280 datasheet(1034/1386 Pages) FREESCALE

1034 / 1386 page

ATM Controller and AAL0, AAL1, and AAL5

MPC8280 PowerQUICC II Family Reference Manual, Rev. 1

31-74

Freescale Semiconductor

31.10.5.10 AAL5 TxBDs

Figure 31-50 shows the AAL5 TxBD.

Table 31-38 describes AAL5 TxBD fields.

23456789

Offset + 0x00

—

CLP CNG

—

Offset + 0x02

Data Length (DL)

Offset + 0x04

Tx Data Buffer Pointer (TXDBPTR)

Offset + 0x06

Figure 31-50. AAL5 TxBD

Table 31-38. AAL5 TxBD Field Descriptions

Offset

Bits

Name

Description

0x00

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.

—

Reserved, should be cleared.

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.

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.

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.

—

Reserved, should be cleared.

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.

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.

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