LAN9730 Datasheet, PDF (103/222 Pages) SMSC Corporation – High-Speed Inter-Chip (HSIC) USB 2.0

LAN9730/LAN9730i
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.
Note: If the originating SUSPEND state is SUSPEND2, the host is required to reinitialize the Ethernet PHY reg-
isters.
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.
Note: If the device is deconfigured, the SUSPEND_MODE field in the Power Management Control Register
(PMT_CTL) resets to 10b.
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.
In this state, the MAC can optionally be programmed to detect a Wake On LAN event or Magic Packet event.
GPIO events can be programmed to cause wakeup in this state. If GPIO7 signals the event, the PHY Link Up Enable
(PHY_LINKUP_EN) bit of the General Purpose IO Wake Enable and Polarity Register (GPIO_WAKE) may be examined
to determined whether a PHY Link Up event or Pin event occurred.
The host may take the device out of the SUSPEND0 state at any time.
4.11.2.3 SUSPEND1
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 01b.
Refer to Section 4.12.2.1, "Enabling GPIO Wake Events", and Section 4.12.2.3, "Enabling Link Status Change (Energy
Detect) Wake Events" for detailed instructions on how to program events that cause resumption from the SUSPEND1
state.
In this state, the Ethernet PHY can be optionally programmed for energy detect. GPIO events can also be programmed
to cause wakeup in this state.
The host may take the device out of the SUSPEND1 state at any time.
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DS00001946A-page 103