KSZ8873MLLI Micrel Inc, KSZ8873MLLI Datasheet - Page 24

• Manufacturer Part Number: KSZ8873MLLI
• Description: IC ETHERNET SWITCH 3PORT 64LQFP
• Manufacturer: Micrel Inc

Specifications of KSZ8873MLLI

• Controller Type: Ethernet Switch Controller
• Interface: MII
• Voltage - Supply: 1.8V, 2.5V, 3.3V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: *
• Package / Case: *
• Number Of Primary Switch Ports: 3
• Internal Memory Buffer Size: 32
• Fiber Support: No
• Integrated Led Drivers: Yes
• Phy/transceiver Interface: MII
• Power Supply Type: Analog
• Data Rate (typ): 10/100Mbps
• Vlan Support: Yes
• Operating Temperature (max): 85C
• Operating Temperature (min): -40C
• Mounting: Surface Mount
• Jtag Support: No
• Operating Supply Voltage (max): 1.89/3.465V
• Operating Temperature Classification: Industrial
• Data Rate: 100Mbps
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Current - Supply: -
• Lead Free Status / RoHS Status: Compliant, Lead free / RoHS Compliant

Micrel, Inc.
KSZ8873MLL/FLL/RLL
In addition, the KSZ8873MLL/FLL/RLL features a per-port power down mode. To save power, a PHY port that is not in
use can be powered down via port control register 29 or 45 bit 3, or MIIM PHY register.
Functional Overview: MAC and Switch
Address Lookup
The internal lookup table stores MAC addresses and their associated information. It contains a 1K unicast address table
plus switching information.
The KSZ8873MLL/FLL/RLL is guaranteed to learn 1K addresses and distinguishes itself from hash-based lookup tables,
which depending on the operating environment and probabilities, may not guarantee the absolute number of addresses it
can learn.
Learning
The internal lookup engine updates its table with a new entry if the following conditions are met:
1. The received packet's Source Address (SA) does not exist in the lookup table.
2. The received packet is good; the packet has no receiving errors, and is of legal length.
The lookup engine inserts the qualified SA into the table, along with the port number and time stamp. If the table is full, the
last entry of the table is deleted to make room for the new entry.
Migration
The internal lookup engine also monitors whether a station has moved. If a station has moved, it will update the table
accordingly. Migration happens when the following conditions are met:
1. The received packet's SA is in the table but the associated source port information is different.
2. The received packet is good; the packet has no receiving errors, and is of legal length.
The lookup engine will update the existing record in the table with the new source port information.
Aging
The lookup engine updates the time stamp information of a record whenever the corresponding SA appears. The time
stamp is used in the aging process. If a record is not updated for a period of time, the lookup engine removes the record
from the table. The lookup engine constantly performs the aging process and will continuously remove aging records. The
aging period is about 200 seconds. This feature can be enabled or disabled through register 3 (0x03) bit [2].
Forwarding
The KSZ8873MLL/FLL/RLL forwards packets using the algorithm that is depicted in the following flowcharts. Figure 4
shows stage one of the forwarding algorithm where the search engine looks up the VLAN ID, static table, and dynamic
table for the destination address, and comes up with “port to forward 1” (PTF1). PTF1 is then further modified by
spanning tree, IGMP snooping, port mirroring, and port VLAN processes to come up with “port to forward 2” (PTF2), as
shown in Figure 5. The packet is sent to PTF2.
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