MPC8280 datasheet(1119/1386 Pages) FREESCALE

1119 / 1386 page

ATM AAL2

MPC8280 PowerQUICC II Family Reference Manual, Rev. 1

Freescale Semiconductor

33-13

Table 33-2 describes the CPS TxQD fields.

Offset + 0x00

—

BNM

HEC

CPS

TBM

—

Offset + 0x02

TxBD Table Offset In (switched mode only)

Offset + 0x04

TxBD Table Base

Offset + 0x06

Offset + 0x08

TxBD Table Offset Out

Offset + 0x0A

Number of Packets In Queue

Offset + 0x0C

NextQueue

Offset + 0x0E

—

Figure 33-7. CPS Tx Queue Descriptor (TxQD)

Table 33-2. CPS TxQD Field Descriptions

Offset

Bits

Name1

Description

0x00

0–7

—

Reserved for internal use. (Used to save the BD status of the open BD.)

BNM

Buffer not-ready interrupt mask of the TxBD table.

0 The transmit buffer-not-ready event for this queue is masked. (The event is not sent

to the interrupt queue.)

1 The buffer-not-ready event for this queue is enabled.

Switching queue.

0 Normal TX Queue.

1 This TxQD handles a switching queue. The receiver and transmitter share this queue.

HEC

HEC calculation.

0 Transmitter calculates the CPS header HEC.

1 The CPS header HEC is taken as is from the CPS buffer descriptor.

CPS

Sublayer type. For a CPS TxQD, this field must be set.

0 SSSAR or SSTED.

1 CPS packet.

TBM

Transmit buffer interrupt mask.

The transmit buffer event of this queue is masked. (The event is not sent to the

interrupt queue).

The transmit buffer event of this queue is enabled.

13–15

—

Reserved, should be cleared during initialization.

0x02

—

TxBD Table

Offset In

Used only when this queue is used for switching (SW=1). Should be cleared during

initialization.

0x04

—

TxBD Table

Base

This pointer points to the base address of the BD table.

0x08

—

TxBD Table

Offset Out

Holds the offset from the TxBD table base to the next BD to be opened by the

transmitter. Should be cleared during initialization.

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