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Table 10. Receive Descriptor Descriptions

Bit#

Name

Descriptions

RDES0

OWN

Own bit

1: indicates that newly received data can be put into this descriptor

0: Host has not yet processed the received data currently in this descriptor.

30-16

Frame length, including CRC. This field is valid only in a frame’s last descriptor.

Error summary. Logical OR of the following bits:

0: overflow

1: CRC error

6: late collision

7: frame too long

11: runt packet

14: descriptor error

This field is valid only in a frame’s last descriptor.

Descriptor error. This bit is valid only in a frame’s last descriptor.

1: the current valid descriptor is unable to contain the packet being currently received. The

packet is truncated.

13-12

Data type.

00: normal

01: MAC loop-back

10: Transceiver loop-back

11: remote loop-back

These bits are valid only in a frame’s last descriptor.

Runt frame (packet length < 64 bytes). This bit is valid only in a frame’s last descriptor.

Multicast frame. This bit is valid only in a frame’s last descriptor.

First descriptor.

Last descriptor.

Packet Too Long (packet length > 1518 bytes). This bit is valid only in a frame’s last descriptor.

Late collision. Set when collision is active after 64 bytes. This bit is valid only in a frame’s last

descriptor

Frame type. This bit is valid only in a frame’s last descriptor.

0: 802.3 type

1: Ethernet type

Receive watchdog (refer to CSR15, bit 4). This bit is valid only in a frame’s last descriptor.

reserved

Default = 0

Dribble bit. This bit is valid only in a frame’s last descriptor

1: Packet length is not integer multiple of 8-bit.

1: CRC error. This bit is valid only in a frame’s last descriptor

1: Overflow. This bit is valid only in a frame’s last descriptor

RDES1

31~26

---

reserved

RER

Receive end of ring. Indicates this descriptor is last, return to base address of descriptor

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