KSZ8995X Micrel Inc, KSZ8995X Datasheet - Page 20

• Manufacturer Part Number: KSZ8995X
• Description: 5 Port 10/100 Switch With PHY And Frame Buffers
• Manufacturer: Micrel Inc

Specifications of KSZ8995X

• 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: 576-1041

KS8995X
Micrel
100BaseFX Signal Detection
The physical port runs in 100BaseFX mode if FXSDx >0.6V for ports 4 and 5 only. This signal is internally referenced to
1.25V.The fiber module interface should be set by a voltage divider such that FXSDx ‘H’ is above this 1.25V reference,
indicating signal detect, and FXSDx ‘L’ is below the 1.25V reference to indicate no signal. When FXSDx is below 0.6V then
100BaseFX mode is disabled.
100BaseFX Far End Fault
Far end fault occurs when the signal detection is logically false from the receive fiber module. When this occurs, the
transmission side signals the other end of the link by sending 84 1’s followed by a zero in the idle period between frames. The
far end fault may be disabled through register settings.
10BaseT Transmit
The output 10BaseT driver is incorporated into the 100BaseT driver to allow transmission with the same magnetics. They are
internally wave-shaped and pre-emphasized into outputs with a typical 2.3V amplitude. The harmonic contents are at least
27dB below the fundamental when driven by an all-ones Manchester-encoded signal.
10BaseT Receive
On the receive side, input buffer and level detecting squelch circuits are employed. A differential input receiver circuit and a
PLL perform the decoding function. The Manchester-encoded data stream is separated into clock signal and NRZ data. A
squelch circuit rejects signals with levels less than 400mV or with short pulsewidths in order to prevent noises at the RXP or
RXM input from falsely triggering the decoder. When the input exceeds the squelch limit, the PLL locks onto the incoming signal
and the KS8995X decodes a data frame. The receiver clock is maintained active during idle periods in between data reception.
Power Management
The KS8995X features a per port power down mode. To save power the user can power down ports that are not in use by setting
port control registers or MII control registers. In addition, it also supports full chip power down mode. When activated, the entire
chip will be shutdown.
MDI/MDI-X Auto Crossover
The KS8995X supports MDI/MDI-X auto crossover. This facilitates the use of either a straight connection CAT-5 cable or a
crossover CAT-5 cable. The auto-sense function will detect remote transmit and receive pairs, and correctly assign the transmit
and receive pairs from the Micrel device. This can be highly useful when end users are unaware of cable types and can also
save on an additional uplink configuration connection. The auto crossover feature may be disabled through the port control
registers.
Auto-Negotiation
The KS8995X conforms to the auto-negotiation protocol as described by the 802.3 committee. Auto-negotiation allows UTP
(Unshielded Twisted Pair) link partners to select the best common mode of operation. In auto-negotiation the link partners
advertise capabilities across the link to each other. If auto-negotiation is not supported or the link partner to the KS8995X is
forced to bypass auto-negotiation, then the mode is set by observing the signal at the receiver. This is known as parallel mode
because while the transmitter is sending auto-negotiation advertisements, the receiver is listening for advertisements or a fixed
signal protocol.
The flow for the link set up is depicted in Figure 4.
20
December 2003
M9999-120403