AX88140AP ETC, AX88140AP Datasheet - Page 34

• Manufacturer Part Number: AX88140AP
• Description: Fast Ethernet MAC Controller
• Manufacturer: ETC

5.3.2 Transmit Descriptor 1 (TDES1)
5.3.3 Transmit Descriptor 2 (TDES2)
5.3.4 Transmit Descriptor 3 (TDES3)
Field
Field
Field
28:27
25:24
22:11
10:0
31:0
31:0
31
30
29
26
23
1
0
AX88140A
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.
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.
LS - Last Segment
FS - First Segment
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.
Reserved.--Written as “0” for future compatibility concern.
DPD - Disabled Padding
The CRC field is added despite the state of
the add CRC disable (TDES1<26>) flag.
Reserved.--Written as “0” for future compatibility concern.
Data Buffer Size
Indicates the size, in bytes, of the data buffer. If this field is 0, the AX88140A ignores this buffer.
Data Buffer Pointer
Physical address of data buffer. There are no limitations on the buffer address alignment.
Address Pointer
Physical address of next descriptor address. There are no limitation on the buffer address alignment.
Tab - 36 Transmit Descriptor 0
Tab - 37 Transmit Descriptor 1
Tab - 38 Transmit Descriptor 2
Tab - 39 Transmit Descriptor 3
1
0
1
0
1
0
Description
Description
Description
34
the AX88140A does not automatically add a padding field,
so a packet shorter than 64 bytes.
The AX88140A automatically adds a padding field and also
a CRC field to a packet shorter than 64 bytes.
Indicates that the buffer contains the last segment of a
frame.
Indicates that the buffer contains the first or middle
segment of a frame.
Indicates that the buffer contains the first segment of a
frame.
Indicates that the buffer contains the middle or last segment
of a frame.
ASIX ELECTRONICS CORPORATION
PRELIMINARY