MPC8280 datasheet(1100/1386 Pages) FREESCALE

1100 / 1386 page

ATM AAL1 Circuit Emulation Service

MPC8280 PowerQUICC II Family Reference Manual, Rev. 1

32-40

Freescale Semiconductor

32.12.2 AAL1 CES TxBDs

Figure 32-29 shows the AAL1 CES TxBD.

Table 32-12 describes AAL1 CES TxBD fields.

0x02

—

Data length. The number of octets the CP writes into the buffer once its BD is closed.

0x04

—

RXDBPTR Rx data buffer pointer. Points to the first location of the associated buffer; may reside in

either internal or external memory. This pointer must be burst-aligned.

012

Offset + 0x00

—

EOSF

—

Offset + 0x02

Data Length (DL)

Offset + 0x04

Tx Data Buffer Pointer (TXDBPTR)

Offset + 0x06

Figure 32-29. AAL1 CES TxBD

Table 32-12. AAL1 CES 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 this bit after the buffer has

been sent or after an error condition is encountered.

1 The buffer prepared for transmission by the user has not been sent or is being sent.

No fields of this BD may be written by the user once R is set.

1—

—

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.

4–5

—

Continuous mode

0 Normal operation.

1 The CP does not clear the ready bit after this BD is closed, allowing the associated

buffer to be retransmitted automatically when the CP next accesses this BD.

7–8

—

Table 32-11. AAL1 CES RxBD Field Descriptions

Offset

Bits

Name

Description

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