net2890 ETC-unknow, net2890 Datasheet - Page 35

• Manufacturer Part Number: net2890
• Description: Interface Controller
• Manufacturer: ETC-unknow

Specification
While the peripheral is connected to the USB, the NET2890 will automatically request suspend mode when
appropriate, as described in section 4.9.
The NET2890 should not be powered-down when its local bus is still connected to a powered-up device.
There are ESD protection circuits in the NET2890 which will short V
not powered, they will sink too much current from the board.
4.11.3 Low-Power Modes
4.11.3.1 USB Suspend (Unplugged from USB)
The NET2890 may draw a small amount of power when un-plugged from the USB. In power-sensitive
applications, the local CPU can force the NET2890 to enter low-power suspend mode when unplugged
from the USB by setting the Suspend Control Bit. The NET2890 will automatically wake-up when the
peripheral is re-connected to the USB. Do not force suspend mode unless the peripheral is unplugged from
the USB. When the NET2890 is connected to the USB, it is a violation of the USB specification to enter the
suspend state unless the upstream port has been idle for at least 3 milliseconds.
This is the preferred method of suspending the NET2890, since a USB plug-in will automatically cause the
NET2890 to wake-up and set the Resume Interrupt Status bit.
4.11.3.2 Power-On Standby
The peripheral can prevent the NET2890 from starting its oscillator on power-up by driving a LOW into the
USBOE# pin from an external open-drain source while RESET# is asserted (LOW). In this state the
NET2890 requires only a small quiescent standby current.
When the peripheral wishes to start the oscillator, it releases the USBOE# line and continues to assert
RESET# for a minimum of 2 milliseconds. Note that while the oscillator is stopped, the NET2890 cannot
respond to USB requests, so the oscillator must be allowed to start when the peripheral detects a USB plug-
in event. Note also that USBOE# should only be driven from an external source while RESET# is asserted.
The NET2890 will not detect a USB plug-in event while in this standby state. The device is responsible for
detecting the plug-in, and ending the standby condition. This standby technique is appropriate when the
device’s power budget does not allow the NET2890 to be active long enough to shut it down by setting the
Suspend Control Bit.
____________________________________________________________________________________
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NetChip Technology, Inc., 1999
Rev 2.0, Draft 9, July 16, 1999
http://www.netchip.com
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NET2890 USB Interface Controller
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pins are
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