KSZ8895MLU_11 Datasheet, PDF (37/110 Pages) Micrel Semiconductor – Integrated 5-Port 10/100 Managed Switch

Micrel, Inc.
KSZ8895MLU
The priority levels in the packets of the 802.1p and DiffServ can be programmed to priority 0  3 by the register 128 and
129 for a re-mapping.
When egress rate limit just use one queue per port for the egress port rate limit, the priority packets will be based on the
data rate selection table with the rate limit exact number. If egress rate limit use more than one queue per port for the
egress port rate limit, the highest priority packets will be based on the data rate selection table for the rate limit exact
number, other lower priority packet rate will be limited based on 8:4:2:1 (default) priority ratio based on the highest priority
rate. The transmit queue priority ratio is programmable.
To reduce congestion, it is a good practice to make sure the egress bandwidth exceeds the ingress bandwidth.
Transmit Queue Ratio Programming
In transmit queues 0  3 of the egress port, the default priority ratio is 8:4:2:1, the priority ratio can be programmed by the
port registers control 10, 11, 12 and 13. When the transmit rate exceed the ratio limit in the transmit queue, the transmit
rate will be limited by the transmit queue 0  3 ratio of the port register control 10, 11, 12 and 13. The highest priority
queue will be no limited, other lower priority queues will be limited based on the transmit queue ratio.
Filtering for Self-Address, Unknown Unicast/Multicast Address and Unknown VID Packet/IP Multicast
Enable Self-address filtering, the unknown unicast packet filtering and forwarding by the Register 131 Global Control 15.
Enable Unknown multicast packet filtering and forwarding by the Register 132 Global Control 16.
Enable Unknown VID packet filtering and forwarding by the Register 133 Global Control 17.
Enable Unknown IP multicast packet filtering and forwarding by the Register 134 Global Control 18.
This function is very useful in preventing those kinds of packets that could degrade the quality of the port in applications
such as voice over Internet Protocol (VoIP) and the daisy chain connection to prevent packets into endless loop.
Configuration Interface
I²C Master Serial Bus Configuration
If a 2-wire EEPROM exists, the KSZ8895MLU can perform more advanced features like broadcast storm protection and
rate control. The EEPROM should have the entire valid configuration data from Register 0 to Register 255 defined in the
“Memory Map,” except the status registers. After reset, the KSZ8895MLU will start to read all 255 registers sequentially
from the EEPROM. The configuration access time (t_prgm) is less than 30ms as shown in Figure 12.
Figure 8. KSZ8895MLU EEPROM Configuration Timing Diagram
October 2011
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M9999-100311-1.1