KSZ8995XA B3 Micrel Inc, KSZ8995XA B3 Datasheet - Page 27

• Manufacturer Part Number: KSZ8995XA B3
• Manufacturer: Micrel Inc

Specifications of KSZ8995XA B3

• Number Of Primary Switch Ports: 5
• Internal Memory Buffer Size: 64
• Operating Supply Voltage (typ): 1.8/2.5/3.3V
• Fiber Support: Yes
• Integrated Led Drivers: Yes
• Phy/transceiver Interface: MII/SNI
• Power Supply Type: Analog/Digital
• Package Type: PQFP
• Data Rate (typ): 10/100Mbps
• Vlan Support: Yes
• Operating Temperature (max): 70C
• Operating Temperature (min): 0C
• Pin Count: 128
• Mounting: Surface Mount
• Jtag Support: No
• Operating Temperature Classification: Commercial
• Lead Free Status / RoHS Status: Compliant

September 2008
The KS8995XA can classify tagged packets using the 802.1p tag-based priority. In this prioritization scheme, the
user can enable the 802.1p classification on a per port basis in bit 5 of registers 0x10, 0x20, 0x30, 0x40 and 0x50 for
ports 1, 2, 3, 4, and 5, respectively. Then the user specifies the 802.1p base priority in register 0x02, bits [6-4]. When
a tagged packet is received, the KS8995XA examines the 3 bit 802.1p priority field shown in Figure 6. These 3 bits
are compared against the base priority. The prioritization policy is as follows:
In order to support QoS from end-to-end in a network, the KS8995XA can also classify packets based on the IPv4
DiffServ field shown in Figure 7.
The DiffServ field consists of 6 bits, which can be used to specify 64 code points. The KS8995XA provides 64 bits
(DSCP[63:0]) in 8 registers (0x60 to 0x67), in which the user specifies the priority of each of the 64 code points. The
DiffServ classification is enabled on a per port basis in bit 6 of registers 0x10, 0x20, 0x30, 0x40 and 0x50 for ports 1,
2, 3, 4, and 5, respectively. If the DiffServ classification is enabled on a port, the KS8995XA will decode the IPv4
DiffServ field and look at the user defined code point bit to determine if the packet is high priority or low priority. If the
code point is a ‘1’, the packet is high priority. If the code point is ‘0’, the packet is low priority.
Bytes
Bytes
Preamble
Preamble
8
8
Comparison
802.1p Priority ≥Base Priority
802.1p Priority < Base Priority
Bits
Ta gged Packet Type
6
(8100 fo r Ethernet)
6
DA
DA
Bits
16
SA
Figure 6. 802.3 Tagged Packet
SA
6
6
Table 4. 802.1p Priority
Figure 7. IPv4 Packet
IP
0x 4
802.1 p
V
4
er.
Ta g
TCI
4
3
4
Length
1
Type
2
2
27
He
Siz
ader
4
LLC
VLAN I D
6
2
e
12
DiffServ
Priority
2
Da ta
High
Low
46-1500
46-1500
Data
Res.
CRC
CRC
4
4
M9999-091508