DS33W41+ Maxim Integrated Products, DS33W41+ Datasheet - Page 69

• Manufacturer Part Number: DS33W41+
• Description: IC MAPPING ETHERNET 256CSBGA
• Manufacturer: Maxim Integrated Products

Specifications of DS33W41+

• Applications: Data Transport
• Interface: Parallel/Serial
• Voltage - Supply: 1.8V, 2.5V, 3.3V
• Package / Case: 256-CSBGA
• Mounting Type: Surface Mount
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

8.16.3 Priority Coding with VLAN Tags (IEEE 802.1p)
The IEEE 802.1Q VLAN tagging standard allocated room for a priority code that was later defined by the IEEE
802.1p standard. IEEE 802.1p eventually became part of IEEE 802.1D.
With Priority Scheduling or Priority Forwarding enabled, the priority value is inspected as each frame arrives on the
Ethernet Interfaces. For IEEE 802.1p priority coding, the priority is located in the 15
The format of the IEEE 802.1p VLAN tagged frame is shown in Figure 8-13. A user-programmed Priority Table is
used to translate the 3-bit 802.1p Priority value into one of four Priority Levels for each Ethernet Interface. The
received PCP value is used as the address for the Priority Table lookup operation. The Priority Levels correspond
to four separate queues. In Priority Forwarding (Forwarding Mode 1), the four queues are in separate WAN
Groups. In Priority Scheduling operation, each WAN Group contains a set of four priority queues. These queues
are collectively referred to as LAN Queues in other portions of this document.
The priority mode (802.1p, DSCP, or none) for each Ethernet port can be independently selected using the
SU.LP1C and SU.LP2C registers. See Section 8.16.6 for more information on programming the priority table.
Figure 8-13. IEEE 802.1Q and 802.1p Field Format
Rev: 063008
Ethernet Byte #
________________________________________________ DS33X162/X161/X82/X81/X42/X41/X11/W41/W11
19+
10
11
12
13
14
15
16
17
18
1
2
3
4
5
6
7
8
9
Bit 7
7
3 Bit PCP Priority
Bit 6
8 (hex)
0 (hex)
Bit 5
Ethernet Type / Length (MSB)
Ethernet Type / Length (LSB)
Destination Address (DA)
Source Address (SA)
Bit 4
CFI
< Data Unit >
8 bits of VLAN ID
Bit 3
11
4 bits of VLAN ID
Bit 2
1 (hex)
0 (hex)
th
byte of the Ethernet frame.
Bit 1
Bit 0
8
0
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