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Functional description of general receive descriptor
The general receive descriptor structure consists of four 32-bit words. If the
timestamp function or IPv4 checksum offload is activated, the enhanced
descriptor must be used.
Receive descriptor word 0 (RXDES0)
Field
Name
R/W
Description
0
PERR_ESA
R/W
Payload Checksum Error / extended status available
When this bit is set, the TCP, UDP or ICMP checksum calculated by
the core does not match the checksum field of the received
encapsulated TCP, UDP or ICMP segment. This bit will also be set
when the number of payload bytes received does not match the
value of the length field of the IPv4 or IPv6 datagram encapsulated
in the received Ethernet frame.
After the enhanced descriptor format is enabled, this bit has ESA
functions.
When ESA is set to 1, it indicates that there is an
extended state in RXDES4.
ESA is valid only when RXDES0[8]=1.
1
CERR
R/W
CRC Error
When this bit is set, a CRC error will occur on the received frame.
This bit is valid only when RXDES0[8]=1
2
DERR
R/W
Dribble Error
When this bit is set, the received frame has a multiple of non-
integer bytes.
This bit is valid only in MII mode.
3
RERR
R/W
Receive Error
When this bit is set and RX_DV signal is transmitted during frame
receiving, RX_ERR signal will be generated.
4
RXWDTTO
R/W
Receive Watchdog Timeout
When this bit is set, the receive watchdog timer has timed out when
receiving the current frame, and the current frame will be truncated
when the watchdog times out.
5
FT
R/W
Frame Type
0: The received frame is an Ethernet type frame
1: The received frame is an IEEE802.3 frame
When this bit is set. When this bit is reset, it indicates that this bit is
invalid for short frames less than 14 bytes.
6
LC
R/W
Late Collision
When this bit is set, a delay collision occurs when a frame is
received in half-duplex mode.
7
IPCERR_TSV
R/W
IPv header Checksum Error / Time Stamp Valid
When this bit is set, there is an error in the IPv4 or IPv6 header.
The reasons may be: the Ethernet type field is inconsistent with the
IP header version field, and does not match the checksum of the
header in IPv4, or the Ethernet frame lacks the required number of
IP header bytes.
After the enhanced descriptor format is enabled, this bit has TSV
functions. When TSV=1, it indicates that the timestamp snapshot
will be written in RXDES6 and RXDES7. TSV is valid only when
RXDES0[8]=1.