KSZ8995XA Micrel Inc, KSZ8995XA Datasheet - Page 28

• Manufacturer Part Number: KSZ8995XA
• Description: IC SWITCH 10/100 5PORT 128PQFP
• Manufacturer: Micrel Inc

Specifications of KSZ8995XA

• 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: 576-1042

September 2008
Once classification of the packets has been determined either by port-based priority, 802.1p tag-based priority or
DiffServ priority, they are placed in either the high or low priority queue on the egress port. The user can enable the
egress priority queues on a per port basis by setting bit 0 of registers 0x10, 0x20, 0x30, 0x40, and 0x50 for ports 1, 2,
3, 4 and 5, respectively. If the egress priority queue for a given port is not set, the port will treat all packets as if they
are the same priority, even though packets are classified on their ingress ports. If the egress priority queue for a
given port is enabled, packets are serviced based on the user programmable egress policy. The priority scheme
selection is set in register 0x05 bits[3-2] as shown in Table 6.
The KS8995XA offers support for port-based, 802.1p tag-based, and IPv4 DiffServ priority, as well as programmable
egress policies. These KS8995XA QoS features enable identifying, classifying and forwarding packets based on their
priority. The system designer is able to use this device to build network elements that give more control over system
resources, priority service to mission critical applications, and can be integrated into the next generation of
multimedia networks.
Rate Limit Support
KS8995XA supports hardware rate limiting on “receive” and “transmit” independently on a per port basis. It also
supports rate limiting in a priority or non-priority environment. The rate limit starts from 0Kbps and goes up to the line
rate in steps of 32Kbps. The KS8995XA uses one second as an interval. At the beginning of each interval, the
counter is cleared to zero, and the rate limit mechanism starts to count the number of bytes during this interval.
DiffServ Field (Binary)
0x05, bit 3
Register
0
0
1
1
000000
000001
000010
000011
000100
111011
111100
111101
111110
111111
•
•
•
0x05, bit 2
Register
0
1
0
1
Table 6. Transmit Priority Ratio
Table 5. DiffServ Code Point
Egress Priority Scheme
Always deliver high priority packets first
Deliver high/low priority packets at a ratio of 10/1
Deliver high/low priority packets at a ratio of 5/1
Deliver high/low priority packets at a ratio of 2/1
Code Point
DSCP[59]
DSCP[60]
DSCP[61]
DSCP[62]
DSCP[63]
DSCP[0]
DSCP[1]
DSCP[2]
DSCP[3]
DSCP[4]
•
•
•
28
KS8995X (Reg. and Bit)
0x67, bit 0
0x67, bit 1
0x67, bit 2
0x67, bit 3
0x67, bit 4
0x60, bit 3
0x60, bit 4
0x60, bit 5
0x60, bit 6
0x60, bit 7
•
•
•
M9999-091508