KSZ8995MA B3 Micrel Inc, KSZ8995MA B3 Datasheet - Page 31

• Manufacturer Part Number: KSZ8995MA B3
• Manufacturer: Micrel Inc

Specifications of KSZ8995MA B3

• 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: Compliant

Semptember 2008
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 Table 3.
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
Spanning Tree Support
Port 5 is the designated port for spanning tree support.
The other ports (port 1 – port 4) can be configured in one of the five spanning tree states via “transmit enable,”
“receive enable,” and “learning disable” register settings in Registers 18, 34, 50, and 66 for ports 1, 2, 3, and 4,
respectively. The following description shows the port setting and software actions taken for each of the five
spanning tree states.
Disable state: the port should not forward or receive any packets. Learning is disabled.
Port setting: "transmit enable = 0, receive enable = 0, learning disable = 1."
Software action: the processor should not send any packets to the port. The switch may still send specific packets to
the processor (packets that match some entries in the static table with “overriding bit” set) and the processor should
discard those packets. Note: processor is connected to port 5 via MII interface. Address learning is disabled on the
port in this state.
Blocking state: only packets to the processor are forwarded. Learning is disabled.
Port setting: "transmit enable = 0, receive enable = 0, learning disable = 1"
Software action: the processor should not send any packets to the port(s) in this state. The processor should
program the “Static MAC table” with the entries that it needs to receive (e.g., BPDU packets). The “overriding” bit
should also be set so that the switch will forward those specific packets to the processor. Address learning is
disabled on the port in this state.
Listening state: only packets to and from the processor are forwarded. Learning is disabled.
Port setting: "transmit enable = 0, receive enable = 0, learning disable = 1.
"Software action: The processor should program the static MAC table with the entries that it needs to receive (e.g.
BPDU packets). The “overriding” bit should be set so that the switch will forward those specific packets to the
processor. The processor may send packets to the port(s) in this state, see “Special Tagging Mode” section for
details. Address learning is disabled on the port in this state.
SNI Signal
TXEN
TXD
TXC
COL
CRS
RXD
RXC
Serial Transmit Data
Serial Receive Data
Table 3. SNI Signals
Collision Detection
Transmit Enable
Transmit Clock
Receive Clock
Carrier Sense
Description
31
KS8995MA/FQ
SMTXD[0]
SMRXD[0]
SMRXDV
SMTXEN
SMRXC
SMTXC
Signal
SCOL
M9999-091508