KSZ8995XA Micrel Inc, KSZ8995XA Datasheet - Page 21

• 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

Functional Overview: Switch Core
Address Look-Up
The internal look-up table stores MAC addresses and their associated information. It contains a 1K unicast address table plus
switching information. The KS8995XA is guaranteed to learn 1K addresses and distinguishes itself from hash-based look-up
tables which, depending on the operating environment and probabilities, may not guarantee the absolute number of addresses
it can learn.
Learning
The internal look-up engine will update its table with a new entry if the following conditions are met:
The look-up engine will insert the qualified SA into the table, along with the port number, time stamp. If the table is full, the
last entry of the table will be deleted first to make room for the new entry.
Migration
The internal look-up engine also monitors whether a station is moved. If it happens, it will update the table accordingly.
Migration happens when the following conditions are met:
The look-up engine will update the existing record in the table with the new source port information.
Aging
The look-up engine will update 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 look-up engine will remove the record from
the table. The look-up engine constantly performs the aging process and will continuously remove aging records. The aging
period is 300 ±75 seconds. This feature can be enabled or disabled through register 3 or by external pull-up or pull-down
resistors on LED[5][2]. See “Register 3” section.
Switching Engine
The KS8995XA features a high performance switching engine to move data to and from the MAC’s packet buffers. It operates
in store and forward mode, while the efficient switching mechanism reduces overall latency.
The KS8995XA has a 64kB internal frame buffer. This resource is shared between all five ports. The buffer sharing mode can
be programmed through Register 2. See “Register 2.” In one mode, ports are allowed to use any free buffers in the buffer pool.
In the second mode, each port is only allowed to use 1/5 of the total buffer pool. There are a total of 512 buffers available. Each
buffer is sized at 128B.
May 2005
KS8995XA
• The received packet’s source address (SA) does not exist in the look-up table.
• The received packet is good; the packet has no receiving errors, and is of legal length.
• The received packet’s SA is in the table but the associated source port information is different.
• The received packet is good; the packet has no receiving errors, and is of legal length.
Force Link Setting
and Set Link Mode
Auto-Negotiation
Negotiation
Start Auto
Bypass
Yes
Figure 4. Auto-Negotiation
Auto-Negotiation
Attempt
No
21
100BaseTX Idles
Link Mode Set ?
Link Mode Set
Listen for
Join Flow
Operation
Parallel
Yes
Listen for 10BaseT
Link Pulses
No
M9999-051305
Micrel, Inc.