LAN89730 datasheet(102/218 Pages) MICROCHIP

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LAN89730

DS60001348A-page 102

 2013-2015 Microchip Technology Inc.

4.11.1

NORMAL STATE

The NORMAL state is the fully functional state of the device. The are two flavors of the NORMAL state, NORMAL Con-

figured and NORMAL Unconfigured. In the Configured variation, all chip subsystem modules are enabled. The Uncon-

figured variation has only a subset of the modules enabled. The reduced functionality allows for power savings.

This NORMAL state is entered by any of the following methods:

• A system reset is asserted.

• The device is suspended and the host issues resume signaling.

• The device is suspended and a wake event is detected.

4.11.1.1

Unconfigured

Upon initially entering the NORMAL state, the device is unconfigured. The device transitions to the NORMAL Configured

state upon the host completion of the USB configuration.

It is possible for the device to be deconfigured by the host after being placed in the NORMAL Configured state, via a

set_configuration command. In this case, the CPM must place the device back into the NORMAL Unconfigured state.

4.11.1.2

Reset Operation

After a system reset, the device is placed into the NORMAL Unconfigured state. When in the NORMAL state, the

READY bit in the Power Management Control Register (PMT_CTL) is set. This READY bit is useful to the host after a

USB reset occurs. In this case, it indicates that the values in the EEPROM have been completely loaded.

4.11.1.3

Suspend Operation

When returning to the NORMAL state from the SUSPEND state, the USB context is maintained. After entering the NOR-

MAL state, the READY bit in the PMT_CTL register is asserted.

4.11.2

SUSPEND STATES

The SUSPEND state is entered after the USB host suspends the device. Four variations of the USB SUSPEND state

are available. Each state offers different options in terms of power consumption and wakeup support.

A SUSPEND state is entered via a transition from the NORMAL state. The SUSPEND_MODE field in the Power Man-

agement Control Register (PMT_CTL) indicates which SUSPEND state is to be used. The host sets the value of this

field to select the desired SUSPEND state, then sends suspend signaling. A transfer back to the NORMAL state occurs

when the host sends resume signaling or a wakeup event is detected.

The device can be suspended from the NORMAL Unconfigured state. In this scenario, it is only possible to transition to

the SUSPEND2 state. Subsequent resume signaling or a wakeup event will cause the device to transition back to the

NORMAL Unconfigured state.

4.11.2.1

Reset from Suspend

All suspend states must respond to a USB Reset and pin reset, nRESET. The application of these resets result in the

device’s hardware being re-initialized and placed into the NORMAL Unconfigured state.

4.11.2.2

SUSPEND0

This state is entered from the NORMAL state when the device is suspended and the SUSPEND_MODE field in the

Power Management Control Register (PMT_CTL) is set to 00b.

Refer to Section 4.12.2.1, "Enabling GPIO Wake Events", Section 4.12.2.2, "Enabling WOL Wake Events" and Section

4.12.2.4, "Enabling External PHY Link Up Wake Events" for detailed instructions on how to program events that cause

resumption from the SUSPEND0 state.

Note:

If the originating SUSPEND state is SUSPEND2, the host is required to reinitialize the Ethernet PHY reg-

isters.

Note:

If the device is deconfigured, the SUSPEND_MODE field in the Power Management Control Register

(PMT_CTL) resets to 10b.

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