KSZ8995X Micrel Inc, KSZ8995X Datasheet - Page 26

• Manufacturer Part Number: KSZ8995X
• Description: 5 Port 10/100 Switch With PHY And Frame Buffers
• Manufacturer: Micrel Inc

Specifications of KSZ8995X

• Applications: *
• Mounting Type: Surface Mount
• Package / Case: 128-MQFP, 128-PQFP
• 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: Lead free / RoHS Compliant
• For Use With: 576-1642 - BOARD EVALUATION FOR KSZ8995XA
• Lead Free Status / RoHS Status: Compliant, Lead free / RoHS Compliant
• Other names: 576-1041

KS8995X
The KS8995X 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 KS8995X examines the 3 bit 802.1p priority field shown in Figure 8. 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 KS8995X can also classify packets based on the IPv4 DiffServ field
shown in Figure 9.
The DiffServ field consists of 6 bits, which can be used to specify 64 code points. The KS8995X 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 KS8995X 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.
M9999-120403
Comparison
802.1p Priority
802.1p Priority < Base Priority
Bytes
Bytes
Base Priority
Preamble
Preamble
8
8
Bits
Tagged Packet Type
(8100 for Ethernet)
DA
DA
6
6
Bits
16
Figure 8. 802.3 Tagged Packet
SA
SA
6
6
Table 4. 802.1p Priority
Low
Priority
High
Figure 9. IPv4 Packet
IP
0x4
802.1p
V
4
Tag
er.
TCI
4
3
4
Length
26
1
Type
2
2
He
Siz
4
ader
LLC
VLAN ID
2
e
6
12
DiffServ
Data
2
46-1500
46-1500
Data
Res.
CRC
CRC
4
4
December 2003
Micrel