AX88140AP ETC, AX88140AP Datasheet - Page 33

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

5.3 Transmit Descriptors
Providing one buffer, one byte-count buffer, and two address pointers in each descriptor .
5.3.1 Transmit Descriptor 0 (TDES0)
TDES0 contains transmitted frame status and descriptor ownership information.
TDES0
TDES1
TDES2
TDES3
Transmit Descriptor Format
Field
30:16
13:12
6:3
31
15
14
11
10
9
8
7
2
AX88140A
OWN - Own Bit
Reserved.--Written as “0” for future compatibility concern.
ES - Error Summary
Indicates the logical OR of the following bits :
TDES0<1>
TDES0<8>
TDES0<9>
TDES0<10>
TDES0<11>
TDES0<14>
TO - Transmit Jabber Time-out : Active high.
The transmission process is aborted and placed in the STOPPED state.
When TDES0<14> is set any heartbeat fail indication (TDES0<7>) is not valid.
Reserved.--Written as “0” for future compatibility concern.
LO - Loss of Carrier during transmission. Active high. (The status is no meaning except 10BASE SRL mode)
Not valid in internal loop-back mode (REG6<11:10>=01).
NC - No Carrier. Indicates that the carrier signal from the transceiver was not present during transmission.
Active high.
Not valid in internal loop-back mode (REG6<11:10>=01).
LC - Late Collision. When set, indicates that the frame transmission was aborted due to collision occurring after
the collision window of 64 bytes. Not valid if under-flow error (TDES0<1>) is set.
EC - Excessive Collision When set, indicates that the transmission was aborted after 16 successive collisions
while attempting to transmit the current frame.
HF - Heartbeat Fail
This bit is effective only in 10Mb/s operation mode. When set, indicates a heartbeat collision check failure
This bit is not valid if under-flow error (TDES0<1>) is set.
On the second transmission attempt, after the first transmission was aborted due to collision, the AX88140A
does not check heartbeat fail and (TDES0<7>) is reset.
CC - Collision Count
This 4-bit counter indicates the number of collisions that occurred before the frame was transmitted.
Not valid when the excessive collisions bit (TDES0<8>) is also set.
Reserved.--Written as “0” for future compatibility concern.
31
O
W
N
Control bits
Fig - 6 Transmit Descriptor Format
Buffer Address 1
Buffer Address 2
Byte Count Buffer 2
under-flow error
successive collisions
late collision
no carrier
loss of carrier
transmit jabber time-out
Description
1
0
33
Indicates that the descriptor is owned by the AX88140A.
Indicates that the descriptor is owned by the host.
Status
ASIX ELECTRONICS CORPORATION
Byte Count Buffer 1
PRELIMINARY
0