KS8993F Micrel Inc, KS8993F Datasheet - Page 34

• Manufacturer Part Number: KS8993F
• Description: IC CONV MED 10/100 3PORT 128PQFP
• Manufacturer: Micrel Inc

Specifications of KS8993F

• Applications: *
• Mounting Type: Surface Mount
• Package / Case: 128-MQFP, 128-PQFP
• Number Of Primary Switch Ports: 3
• Internal Memory Buffer Size: 32
• 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 Supply Voltage (max): 1.89/3.465V
• Operating Temperature Classification: Commercial
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• For Use With: KS8993F-EVAL - EVAL KIT EXPERIMENTAL KS8993F
• Lead Free Status / RoHS Status: Not Compliant, Lead free / RoHS Compliant

On the transmit side, the KS8993F has intelligent and efficient means to determine when to invoke flow control. The
flow control is based on the availability of system resources, including available buffers, available transmit queues and
available receive queues.
The KS8993F will flow control a port, which just received a packet, if the destination port resource is being used up.
The KS8993F will issue a flow control frame (XOFF), containing the maximum pause time defined in IEEE standard
802.3x. Once the resource is freed up, the KS8993F will send out the other flow control frame (XON) with zero pause
time to turn off the flow control (turn on transmission to the port). A hysteresis feature is provided to prevent the flow
control mechanism from being activated and deactivated too many times.
The KS8993F will flow control all ports if the receive queue becomes full.
2.4.12 Half Duplex Back Pressure
A half-duplex back-pressure option (Note: not in IEEE 802.3 standards) is also provided.
deactivation conditions are the same as the above in full duplex mode. If back-pressure is required, the KS8993F will
send preambles to defer the other stations' transmission (carrier sense deference). To avoid jabber and excessive
deference defined in 802.3 standard, after a certain time it will discontinue the carrier sense but it will raise the carrier
sense quickly. This short silent time (no carrier sense) is to prevent other stations from sending out packets and keeps
other stations in carrier sense deferred state.
carrier sense type back-pressure will be interrupted and those packets will be transmitted instead. If there are no more
packets to send, carrier sense type back-pressure will be active again until switch resources free up. If a collision
occurs, the binary exponential back-off algorithm is skipped and carrier sense is generated immediately, reducing the
chance of further colliding and maintaining carrier sense to prevent reception of packets.
To ensure no packet loss in 10 BASE-T or 100 BASE-TX half duplex modes, the following should be enabled:
These bits are not set as defaults because the settings are not part of the IEEE standard.
2.4.13 Broadcast Storm Protection
The KS8993F 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 KS8993F 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 67ms interval for 100BT and a 500 ms 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 Global Registers 6 (0x06) and 7 (0x07). The default setting for registers
6 and 7 is 0x63, which is 99 decimal. This is equal to a rate of 1 %, calculated as follows:
148,800 frames/sec * 67 ms/interval * 1% = 99 frames/interval (approx.) = 0x63h
This means the KS8993F accepts only 1% of broadcast data and filters out 99%.
2.5
Micrel, Inc.
June 2009
MII Interface Operation
1. Aggressive back off (set Global Register 3 (0x03), bit 0 to ‘1’, or pull high SMAC (pin 69))
2. No excessive collision drop (set Global Register 4 (0x04), bit 3 to ‘1’, or pull high SMAC (pin 69))
If the port has packets to send during a back-pressure situation, the
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The activation and
or [phone]
M9999-062509
KS8993F/FL