AX88141

PRELIMINARY

ASIX ELECTRONICS CORPORATION

32

CONFIDENTIAL

1

UF - Under-flow Error

When set, indicates that the transmitter aborted the message because data arrived late from memory. Under-flow error indicates

that the AX88141 encountered an empty transmit FIFO while transmitting a frame. The transmission process enters the

suspended state and sets both transmit under-flow (REG5<0>) and transmit interrupt (REG5<0>).

0

DE - Deferred

When set, indicates that the AX88141 had to defer while ready to transmit a frame because the carrier was asserted.

Tab - 42 Transmit Descriptor 0

5.3.2 Transmit Descriptor 1 (TDES1)

Field

Description

31

IC - Interrupt on Completion

When set, the AX88141 sets transmit interrupt (REG5<0>) after the present frames has been transmitted. It is valid only when

first segment (TDES1<30>) is set.

1

Indicates that the buffer contains the last segment of a frame.

30

LS - Last Segment

0

Indicates that the buffer contains the first or middle segment of a frame.

1

Indicates that the buffer contains the first segment of a frame.

29

FS - First Segment

0

Indicates that the buffer contains the middle or last segment of a frame.

28:27

Reserved.--Written as “0” for future compatibility concern.

26

AC - Add CRC Disable

When set, the AX88141 does not append the CRC to the end of the transmitted frame. This field is valid only when first segment

(TDES1<29>) is set.

25:24

Reserved.--Written as “0” for future compatibility concern.

1

the AX88141 does not automatically add a padding field, so a packet

shorter than 64 bytes.

23

DPD - Disabled Padding

The CRC field is added despite the state of

the add CRC disable (TDES1<26>) flag.

0

The AX88141 automatically adds a padding field and also a CRC field to a

packet shorter than 64 bytes.

22:11

Reserved.--Written as “0” for future compatibility concern.

10:0

Data Buffer Size

Indicates the size, in bytes, of the data buffer. If this field is 0, the AX88141 ignores this buffer.

Tab - 43 Transmit Descriptor 1

5.3.3 Transmit Descriptor 2 (TDES2)

Field

Description

31:0

Data Buffer Pointer

Physical address of data buffer. There are no limitations on the buffer address alignment.

Tab - 44 Transmit Descriptor 2

5.3.4 Transmit Descriptor 3 (TDES3)

Field

Description

31:0

Address Pointer

Physical address of next descriptor address. There are no limitation on the buffer address alignment.

Tab - 45 Transmit Descriptor 3