KSZ8995XA Micrel Inc, KSZ8995XA Datasheet - Page 23

• 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

Broadcast Storm Protection
The KS8995XA has an intelligent option to protect the switch system from receiving too many broadcast packets. Broadcast
packets will be forwarded to all ports except the source port, and thus use too many switch resources (bandwidth and available
space in transmit queues). The KS8995XA has the option to include “multicast packets” for storm control. The broadcast storm
rate parameters are programmed globally, and can be enabled or disabled on a per port basis. The rate is based on a 50ms
interval for 100BT and a 500ms interval for 10BT. 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 the interval. The rate definition is described in Register 6 and
Register 7. The default setting for registers 6 and 7 is 0x4A, which is 74 decimal. This is equal to a rate of 1%, calculated as
follows:
MII Interface Operation
The media independent interface (MII) is specified by the IEEE 802.3 committee and provides a common interface between
physical layer and MAC layer devices. The KS8995XA provides two such interfaces. The MII-P5 interface is used to connect
to the fifth PHY, whereas the MII-SW interface is used to connect to the fifth MAC. Each of these MII interfaces contains two
distinct groups of signals, one for transmission and the other for receiving. The table below describes the signals used in the
MII-P5 interface.
The MII-P5 interface operates in PHY mode only, while the MII-SW interface operates in either MAC mode or PHY mode. These
interfaces are nibble-wide data interfaces and therefore run at 1/4 the network bit rate (not encoded). Additional signals on the
transmit side indicate when data is valid or when an error occurs during transmission. Likewise, the receive side has indicators
that convey when the data is valid and without physical layer errors. For half-duplex operation, there is a signal that indicates
a collision has occurred during transmission.
Note that the signal MRXER is not provided on the MII-SW interface for PHY mode operation and the signal MTXER is not
provided on the MII-SW interface for MAC mode operation. Normally MRXER would indicate a receive error coming from the
physical layer device. MTXER would indicate a transmit error from the MAC device. These signals are not appropriate for this
configuration. For PHY mode operation, if the device interfacing with the KS8995XA has an MRXER pin, it should be tied low.
For MAC mode operation, if the device interfacing with the KS8995XA has an MTXER pin, it should be tied low.
May 2005
KS8995XA
148,800 frames/sec × 50ms/interval × 1% = 74 frames/interval (approx.) = 0x4A
MII Signal
MRXDV
MRXER
MTXEN
MTXER
MRXD3
MRXD2
MRXD1
MRXD0
MTXD3
MTXD2
MTXD1
MTXD0
MCRS
MRXC
MTXC
MCOL
MDIO
MDC
Table 1. MII – P5 Signals (PHY Mode)
Management data clock
Management data I/O
Transmit data bit 3
Transmit data bit 2
Transmit data bit 1
Transmit data bit 0
Collision detection
Receive data valid
Receive data bit 3
Receive data bit 2
Receive data bit 1
Receive data bit 0
Transmit enable
Transmit clock
Transmit error
Receive clock
Carrier sense
Receive error
Description
23
KS8995XA Signal
PMRXD[3]
PMRXD[2]
PMRXD[1]
PMRXD[0]
PMTXD[3]
PMTXD[2]
PMTXD[1]
PMTXD[0]
PMRXDV
PMRXER
PMTXEN
PMTXER
PMRXC
PMTXC
PCOL
PCRS
MDIO
MDC
M9999-051305
Micrel, Inc.