Receive and Transmit Description

Receive

 

Descriptor Error

Description

bits

 

 

 

 

Sequence Error

 

When set, indicates a received packet with a bad delimiter sequence (in TBI mode/

 

internal SerDes). In other 802.3 implementations, this would be classified as a

SEQ (bit 2)

framing error.

 

A valid delimiter sequence consists of:

 

idle start-of-frame (SOF) data, pad (optional) end-of-frame (EOF) fill

 

(optional) idle.

 

 

SE (bit 1)

Symbol Error

When set, indicates a packet received with bad symbol. Applicable only in TBI mode/

 

internal SerDes.

 

 

CE (bit 0)

CRC Error or Alignment Error

CRC errors and alignment errors are both indicated via the CE bit. Software may

 

distinguish between these errors by monitoring the respective statistics registers.

 

 

a. Not applicable to the 82540EP/EM, 82541xx, or 82547GI/EI.

3.2.3.3Receive Descriptor Special Field

Hardware stores additional information in the receive descriptor for 802.1q packets. If the packet type is 802.1q, determined when a packet type field matches the VLAN1 Ethernet Register (VET) and RCTL.VME = 1b, then the special field records the VLAN information and the four byte VLAN information is stripped from the packet data storage. The Ethernet controller stores the Tag Control Information (TCI) of the 802.1q tag in the Special field. Otherwise, the special field contains 0000h.

Table 3-4. Special Descriptor Field Layout

802.1q Packets

15

13

12

11

0

PRI

CFI

VLAN

All Other Packets

15

8 7

0

00

00

Receive

 

Descriptor

Description

Special Field

 

 

 

VLAN

VLAN Identifier

12 bits that records the packet VLAN ID number

 

 

 

CFI

Canonical Form Indicator

1 bit that records the packet’s CFI VLAN field

 

 

 

PRI

User Priority

3 bits that records the packet’s user priority field.

 

 

 

1.Not applicable to the 82541ER.

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Software Developer’s Manual

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Intel Intel Gigabit Ethernet Controllers Receive Descriptor Special Field, Special Descriptor Field Layout, PRI CFI Vlan