AX88140AP datasheet(34/46 Pages) ASIX

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AX88140A

PRELIMINARY

ASIX ELECTRONICS CORPORATION

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 AX88140A 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>).

DE - Deferred

When set, indicates that the AX88140A had to defer while ready to transmit a frame because the carrier was

asserted.

Tab - 36 Transmit Descriptor 0

5.3.2 Transmit Descriptor 1 (TDES1)

Field

Description

IC - Interrupt on Completion

When set, the AX88140A sets transmit interrupt (REG5<0>) after the present frames has been transmitted. It is

valid only when first segment (TDES1<30>) is set.

Indicates that the buffer contains the last segment of a

frame.

LS - Last Segment

Indicates that the buffer contains the first or middle

segment of a frame.

Indicates that the buffer contains the first segment of a

frame.

FS - First Segment

Indicates that the buffer contains the middle or last segment

of a frame.

28:27

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

AC - Add CRC Disable

When set, the AX88140A 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.

the AX88140A does not automatically add a padding field,

so a packet shorter than 64 bytes.

DPD - Disabled Padding

The CRC field is added despite the state of

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

The AX88140A 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 AX88140A ignores this buffer.

Tab - 37 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 - 38 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 - 39 Transmit Descriptor 3

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