Altera Cyclone V Device Handbook page 888

cv_54017
2013.12.30
Bit
25
24
23:22
21
20
19:18
17
16
Ethernet Media Access Controller
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TTSE: Transmit Timestamp Enable
When set, this bit enables IEEE1588 hardware timestamping for the transmit frame
referenced by the descriptor. This field is valid only when the First Segment control bit
(TDES0[28]) is set.
Reserved
CIC: Checksum Insertion Control. These bits control the checksum calculation and insertion.
The following list describes the bit encoding:
■ 0: Checksum Insertion Disabled.
■ 1: Only IP header checksum calculation and insertion are enabled.
■ 2: IP header checksum and payload checksum calculation and insertion are enabled, but
pseudoheader checksum is not calculated in hardware.
■ 3: IP Header checksum and payload checksum calculation and insertion are enabled, and
pseudoheader checksum is calculated in hardware.
This field is valid when the First Segment control bit (TDES0[28]) is set.
TER: Transmit End of Ring
When set, this bit indicates that the descriptor list reached its final descriptor. The DMA
returns to the base address of the list, creating a descriptor ring.
TCH: Second Address Chained
When set, this bit indicates that the second address in the descriptor is the Next descriptor
address rather than the second buffer address. When TDES0[20] is set, TBS2 (TDES1[28:16])
is a "don't care" value.
TDES0[21] takes precedence over TDES0[20].
Reserved
TTSS: Transmit Timestamp Status
This field is used as a status bit to indicate that a timestamp was captured for the described
transmit frame. When this bit is set, TDES2 and TDES3 have a timestamp value captured
for the transmit frame. This field is only valid when the descriptor's Last Segment control
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bit (TDES0[29]) is set.
IHE: IP Header Error
When set, this bit indicates that the MAC transmitter detected an error in the IP datagram
header. The transmitter checks the header length in the IPv4 packet against the number of
header bytes received from the application and indicates an error status if there is a
mismatch. For IPv6 frames, a header error is reported if the main header length is not 40
bytes. Furthermore, the Ethernet Length/Type field value for an IPv4 or IPv6 frame must
match the IPheader version received with the packet. For IPv4 frames, an error status is
also indicated if the Header Length field has a value less than 0x5.
Transmit Descriptor
Description
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17-39
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