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AT32F435/437
Series Reference Manual
2022.11.11
Page 598
Rev 2.03
Figure 26-13 RXDMA descriptor structure
O
W
N
Status [30:0]
Contr
ol
Buffer 1 address [31:0]
Buffer 2 address [31:0] or next descriptor address[31:0]
Rers.
[30:29]
Buffer 2 byte count [28:16]
Control
[15:14]
Rers.
31
0
RDES 0
RDES 1
RDES 2
RDES 3
Buffer 1 byte count [12:0]
RDES0: Receive descriptor word0
RDES0 contains the receive frame state, the frame length and the descriptor ownership information.
Bit
Name
Type
Description
Bit 31
OWN
rw
Own bit
0: The descriptor is owned by the CPU
1: The descriptor is owned by the DMA
This bit is cleared by the DMA when the DMA completes the frame transmission or
when the buffers associated with this descriptor are full. The descriptor is released
to the CPU.
Bit 30
AFM
rw
Destination address filter fail
When set, this bit indicates that a frame failed the DA filter in the MAC core.
Bit 29: 16 FL
rw
Frame length
These bits indicate the byte length of the received frame that was transferred to the
system memory by the DMA. This field is valid only when the LS bit (RESD0[8]) is
set and descriptor error bit is cleared (RDES0[14). If the LS bit is cleared, this field
indicates the accumulated number of bytes that have been transferred to the system
memory. Whether the frame length includes CRC depends on the bit 7 and bit 25 in
the EMAC_MACCTRL register.
Bit 15
ES
rw
Error summary
This bit indicates the logical OR of the following bits:
RDES0[1]: CRC error
RDES0[3]: Receive error
RDES0[4]: Watchdog timeout
RDES0[6]: Late collision
RDES0[7]: Giant frame or IP checksum error
RDES0[11]: Overflow error
RDES0[14]: Descriptor error
Bit 14
DE
rw
Descriptor error
When set, this bit indicates a frame truncation caused by a frame that does not fit
with the current descriptor buffers, and that the DMA does not own the next
descriptor. This bit is valid only when the LS bit (RDES0[8])) is set.
Bit 13
SAF
rw
Source address filter fail
When set, this bit indicates that the received frame failed the SA filter in the MAC
core.
Bit 12
LE
rw
Length error
When set, this bit indicates that the actual length of the received frame does not
match the value in the Ethernet length/type field. This bit is valid only when the
RDES0[5] bit is cleared. It is invalid when a CRC error occurs.
Bit 11
OE
rw
Overflow error
When set, this bit indicates that the received frame was damaged due to receive
FIFO overflow.
Bit 10
VLAN
rw
VLAN tag
When set, this bit indicates that the frame pointed to by the current descriptor is
marked as a VLAN frame by the MAC.
Bit 9
FS
rw
First descriptor
When set, this bit indicates that this descriptor contains the first buffer of the frame.
If the size of the first buffer is 0, the second buffer contains the beginning of the
frame. If the size of the second buffer is also 0, the buffer of the next descriptor