MPC8280 datasheet(1123/1386 Pages) FREESCALE

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ATM AAL2

MPC8280 PowerQUICC II Family Reference Manual, Rev. 1

Freescale Semiconductor

33-17

Table 33-4 describes the SSSAR TxQD fields.

Table 33-4. SSSAR TxQD Field Descriptions

Offset

Bits

Name1

Boldfaced entries must be initialized by the user.

Description

0x00

0–7

—

Reserved, should be cleared during initialization.

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.

UUI

UUI insertion mode

0 UUI of last CPS packet is 0.

1 UUI of last CPS packet is taken from the next byte after the end of the buffer.2

The 5-bit UUI field is inserted into the header of the last packet of an SSSAR SDU. The user must append the UUI to

the last buffer as an additional byte. This additional byte is then inserted into the UUI field of the last packet header

(note that, it is important that this additional byte—the byte after the last byte in the last data buffer of the SSSAR

frame—contains the 5 bits of the UUI). The 3 MSB bits of this extra byte should be cleared; refer to Figure 33-10.

INF

Indicates the current state of the frame.

0 The next packet will be the first of a new frame.

1 Currently in the middle of the frame.

CPS

Sublayer type. For an SSSAR TxQD, this field must be cleared.

0 SSSAR or SSTED.

1 CPS packet.

TBM

Transmit buffer interrupt mask for TxBD table.

0 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.

SSSAR

SSSAR bit

0 SSTED sublayer

1 SSSAR sublayer

14–15

—

Reserved, should be cleared during initialization.

0x02

0–7

Seg_Len

Specifies the maximum length in bytes of the SSSAR PDU (excluding the packet

header). Seg_Len is limited to 45 in NoSTF=1 mode. The CP always attempts to

segment the SSSAR SDU according to this length, but not more than it.

8–15

—

Reserved, should be cleared during initialization.

0x04

—

TxBD Table Base Must be initialized to the first TxBD by the user.

0x08

—

TxBD Table

Offset Out

Used to calculate the pointer to the next TxBD to be used for transmission.

Should be cleared during initialization.

0x0A

—

Reserved, should be cleared during initialization.

0x0C

—

NextQueue

Points to the next TxQD to be serviced after this one. See Section Section 33.3.2,

“Transmit Priority Mechanism.”

0x0E–

0x1E

—

Reserved, should be cleared during initialization.

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