Micrel, Inc.
KSZ8041NL
Power Management
The KSZ8041NL offers the following power management modes:
Power Saving Mode
This mode is used to reduce power consumption when the cable is unplugged. It is in effect when auto-negotiation mode
is enabled, cable is disconnected, and register 1F bit 10 is set to 1. Under power saving mode, the KSZ8041NL shuts
down all transceiver blocks, except for transmitter, energy detect and PLL circuits. Additionally, in MII mode, the RXC
clock output is disabled. RXC clock is enabled after the cable is connected and link is established.
Power saving mode is disabled by writing a zero to register 1F bit 10.
Power Down Mode
This mode is used to power down the entire KSZ8041NL device when it is not in use. Power down mode is enabled by
writing a one to register 0 bit 11. In the power down state, the KSZ8041NL disables all internal functions, except for the
MII management interface.
Reference Clock Connection Options
A crystal or clock source, such as an oscillator, is used to provide the reference clock for the KSZ8041NL. The reference
clock is 25MHz for MII mode and 50MHz for RMII mode. The following two figures illustrate how to connect the reference
clock to XI / REFCLK (pin 9) and XO (pin 8) of the KSZ8041NL.
Figure 4. 25MHz Crystal / Oscillator Reference Clock for MII Mode
Figure 5. 50MHz Oscillator Reference Clock for RMII Mode
July 2008
22
M9999-071808-1.2
MICROCHIP [ MICROCHIP ]
