KSZ8995XA Micrel Inc, KSZ8995XA Datasheet - Page 25

• 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

SNI Interface Operation
The serial network interface (SNI) is compatible with some controllers used for network layer protocol processing. This interface
can be directly connected to these types of devices. The signals are divided into two groups, one for transmission and the other
for reception. The signals involved are described in the table below.
This interface is a bit-wide data interface and therefore runs at the network bit rate (not encoded). An additional signal on the
transmit side indicates when data is valid. Likewise, the receive side has an indicator that conveys when the data is valid.
For half-duplex operation there is a signal that indicates a collision has occurred during transmission.
Advanced Functionality
QoS Support
The KS8995XA is a QoS switch, meaning that is it able to identify selected packets on its ingress ports, prioritize them, and
service the packets according to their priority on the egress ports. In this way, the KS8995XA can provide statistically better
service to the high priority packets that are latency sensitive, or require higher bandwidth. The KS8995XA supports ingress
QoS classification using three different mechanisms: port-based priority, 802.1p tag-based priority, and DSCP priority for IPv4
packets.
Port-based priority is useful when the user wants to give a device on a given port high priority. For example in Figure 7, port
1 is given high priority because it is connected to an IP phone and port 4 is given lower priority because it is connected to a
computer whose data traffic may be less sensitive to network congestion. Each port on the KS8995XA can be set as high or
low priority with an EEPROM. The port priority is set in bit 4 of registers 0x10, 0x20, 0x30, 0x40, 0x50 for ports 1, 2, 3, 4 and
5, respectively. Port-based priority is overridden by the OR’ed result of the 802.1p and DSCP priorities if they are all enabled
at the same time.
May 2005
KS8995XA
SNI Signal
TXEN
TXD
TXC
COL
CRS
RXD
RXC
Description
Transmit Enable
Serial Transmit Data
Transmit Clock
Collision Detection
Carrier Sense
Serial Receive Data
Receive Clock
P5[0]=1, Hi/Lo Tx Priority
Queues enabled
High Priority Port
Figure 7. Port-Based Priority
P1[3]=1
Table 3. SNI Signals
IP Phone
P1
Queue
Hi-Pri
25
WAN
8995XA
P2
Router
P5
Low
Queue
P3
Lo-Pri
P
P
4[3
rio ty
]=0
ri
P4
P
o
rt
KS8995XA Signal
SMTXEN
SMTXD[0]
SMTXC
SCOL
SMRXDV
SMRXD[0]
SMRXC
M9999-051305
Micrel, Inc.