KSZ8864RMNI MICREL [Micrel Semiconductor], KSZ8864RMNI Datasheet - Page 28

• Manufacturer Part Number: KSZ8864RMNI
• Description: Integrated 4-Port 10/100 Managed Switch with Two MACs MII or RMII Interfaces
• Manufacturer: MICREL [Micrel Semiconductor]

September 2011
Energy detect mode consists of two states, normal power state and low power state. While in low power state, the
KSZ8864RMN reduces power consumption by disabling all circuitry except the energy detect circuitry of the receiver.
The energy detect mode is entered by setting bit [4:3] = 01 in register 14. When the KSZ8864RMN is in this mode, it
will monitor the cable energy. If there is no energy on the cable for a time longer than pre-configured value at bit [7:0]
Go-Sleep time in register 15, then the KSZ8864RMN will go into a low power state. When KSZ8864RMN is in low
power state, it will keep monitoring the cable energy. Once the energy is detected from the cable, KSZ8864RMN will
enter normal power state. When KSZ8864RMN is at normal power state, it is able to transmit or receive packet from
the cable.
Soft Power-Down Mode
The soft power-down mode is entered by setting bit [4:3] =10 in register 14. When KSZ8864RMN is in this mode, all
PLL clocks are disabled, also all of PHYs and the MACs are off. Any dummy host access will wake-up this device
from current soft power down mode to normal operation mode and internal reset will be issued to make all internal
registers go to the default values.
Power Saving Mode
The power saving mode is entered when auto-negotiation mode is enabled, cable is disconnected, and by setting bit
[4:3] =11 in register 14. When KSZ8864RMN is in this mode, all PLL clocks are enabled, MAC is on, all internal
registers value will not change, and host interface is ready for CPU read or write. In this mode, it mainly controls the
PHY transceiver on or off based on line status to achieve power saving. The PHY remains transmitting and only turns
off the unused receiver block. Once activity resumes due to plugging a cable or attempting by the far end to establish
link, the KSZ8864RMN can automatically enabled the PHY power up to normal power state from power saving mode.
During this power saving mode, the host CPU can set bit [4:3] in register 14 to transit the current power saving mode
to any one of the other three power management operation modes.
Port-Based Power-Down Mode
In addition, the KSZ8864RMN features a per-port power down mode. To save power, a PHY port that is not in use
can be powered down by the port registers control 13 bit3, or MIIM PHY registers 0 bit11.
Functional Overview: Switch Core
Address Look-Up
The internal look-up table stores MAC addresses and their associated information. It contains a 1K unicast address
table plus switching information. The KSZ8864RMN is guaranteed to learn 1K addresses and distinguishes itself
from a hash-based look-up table which, depending upon the operating environment and probabilities, may not
guarantee the absolute number of addresses it can learn.
Learning
The internal look-up engine updates its table with a new entry if the following conditions are met:
The look-up engine inserts the qualified SA into the table, along with the port number and time stamp. If the table is
full, the last entry of the table is deleted first to make room for the new entry.
Migration
The internal look-up engine also monitors whether a station is moved. If this occurs, it updates the table accordingly.
Migration happens when the following conditions are met:
The look-up engine will update the existing record in the table with the new source port information.
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The received packet’s source address (SA) does not exist in the look-up table.
The received packet is good; the packet has no receiving errors and is of legal length.
The received packet’s SA is in the table but the associated source port information is different.
The received packet is good; the packet has no receiving errors and is of legal length.
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