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Functional Description
893
SLAU723A – October 2017 – Revised October 2018
Copyright © 2017–2018, Texas Instruments Incorporated
Ethernet Controller
Table 15-2. Enhanced Transmit Descriptor 0 (TDES0) (continued)
Bit
Description
19:18
VLIC: VLAN Insertion Control
When set, these bits request the MAC to perform VLAN tagging or untagging before transmitting the frames. If the
frame is modified for VLAN tags, the MAC automatically recalculates and replaces the CRC bytes.
The values of this field are as follows:
• 0x0 = Do not add a VLAN tag
• 0x1 = Remove the VLAN tag from the frames before transmission.
• 0x2 = Insert a VLAN tag with the tag value programmed in the Ethernet MAC VLAN Tag Inclusion or Replacement
(EMACVLNINCREP) register, offset 0x584.
• 0x3 = Replace the VLAN tag in frame with the tag value programmed in the EMACVLNINCREP register. This field
is valid when the First Segment control bit (TDES0[28]) is set.
17
TTSS:TX Timestamp
This status bit indicates that a timestamp has been captured for the corresponding transmit frame. When this bit is set,
TDES6 and TDES7 have timestamp values that were captured for the transmit frame. This field is valid only when the
Last Segment control bit (TDES0[29]) in a descriptor is set.
16
IHE: IP Header Error
When set, this bit indicates that the Checksum Offload engine detected an IP header error. This bit is valid only when
TX Checksum Offload is enabled. Otherwise, it is reserved. If the Checksum Offload Engine detects an IP header error,
it still inserts an IPv4 header checksum if the Ethernet Type field indicates an IPv4 payload.
15
ES: Error Summary
Indicates the logical OR of the following bits:
• TDES0[16]: IP Header Error
• TDES0[14]: Jabber Timeout
• TDES0[13]: Frame Flush
• TDES0[12]: Payload Checksum Error
• TDES0[11]: Loss of Carrier
• TDES0[10]: No Carrier
• TDES0[9]: Late Collision
• TDES0[8]: Excessive Collision
• TDES0[2]: Excessive Deferral
• TDES0[1]: Underflow error
14
JT: Jabber Timeout
When set, this bit indicates that the MAC transmitter has experienced a jabber time-out. This bit can only be set when
the Jabber Disabled (JD) bit of the EMACCFG register is clear.
13
FF: Frame Flushed
When set, this bit indicates that the DMA flushed the frame because of a software flush command given by the CPU.
12
IPE: IP Payload Error
When set, this bit indicates that MAC transmitter detected an error in the TCP, UDP, or ICMP IP datagram payload.
The transmitter checks the payload length received in the IPv4 or IPv6 header against the actual number of TCP, UDP,
or ICMP packet bytes received from the application and issues an error status in case of a mismatch.
11
LC: Loss of Carrier
When set, this bit indicates that Loss of Carrier occurred during frame transmission. This is valid only for the frames
transmitted without collision and when the MAC operates in half-duplex mode.
10
NC: No Carrier
When set, this bit indicates that the carrier sense signal form the PHY was not asserted during transmission.
9
LC: Late Collision
When set, this bit indicates that frame transmission was aborted due to a collision occurring after the collision window
(64 byte times including Preamble in MII Mode). Not valid if Underflow Error (bit 1) is set.
8
Excessive Collision
When set, this bit indicates that the transmission was aborted after 16 successive collisions while attempting to transmit
the current frame. If the Disable Retry (DR) bit in EMACCFG register is set, this bit is set after the first collision and the
transmission of the frame is aborted.
7
VF: VLAN Frame
When set, this bit indicates that the transmitted frame was a VLAN-type frame.
6:3
CC: Collision Count
This 4-bit counter value indicates the number of collisions occurring before the frame was transmitted. The count is not
valid when the Excessive Collision bit (TDES0[8]) is set.