AT43311 データシートの表示（PDF） - Atmel Corporation
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AT43311 Datasheet PDF : 24 Pages
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AT43311
Endpoint0
Endpoint0 is the AT43311’s default endpoint used for enu-
meration of the Hub and exchange of configuration infor-
mation and requests between the Host and the AT43311.
Endpoint0 supports control transfers.
Standard USB Device Requests and class-specific Hub
Requests are supported through Endpoint0.
The Hub Controller supports the following descriptors
through Endpoint0 (Descriptors are described in detail in
the Descriptors Section of this document):
• Device Descriptor
• Configuration Descriptor
• Interface Descriptor
• Endpoint Descriptor
• Hub Descriptor
Endpoint1
Endpoint1 is used by the Hub Controller to send status
change information to the Host. Endpoint1 supports inter-
rupt transfers.
The Hub Controller samples the changes at the end of
every frame at time marker EOF2 in preparation for a
potential data transfer in the subsequent frame. The sam-
pled information is stored as a byte in Status Change Reg-
ister using a bitmap scheme.
Each bit in the Status Change Register corresponds to one
port as shown below.
An IN Token packet from the Host to Endpoint1 indicates a
request for port change status. If the Hub has not detected
any change on the ports or any changes in the hub itself,
then all bits in this register will be 0 and the Hub Controller
will return a NAK to requests on Endpoint1. If a change in
the port status exists, the Hub Controller will transfer the
whole byte. The Hub Controller will continue to report a sta-
tus change when polled until that particular change has
been removed by a ClearPortFeature request from the
Host. No status change will be reported by Endpoint1 until
the AT43311 has been enumerated and configured by the
Host through Endpoint0.
Power Management
The AT43311 is designed to be powered from the USB
bus. As such, the power consumption for the AT43311
itself is less than 100 mA. However, downstream devices
require separate power supplies. The AT43311 monitors
and controls each power supply to the individual down-
stream devices.
Careful design and selection of the power switch is
required to meet the USB specification. The USB specifica-
tions requires that the voltage drop at the power switch be
no more than 100 mV. USB requirements specify that a
downstream device may use a maximum of 500 mA. These
conditions are best met by using a MOSFET switch with an
on resistance of 200 mΩ or less.
As a sample power circuit, consider a P-channel enhance-
ment mode MOSFET. The condition of the port’s power is
monitored at the output side of the PMOS switch which is
connected to the port’s OVL[1:4] pin. During an overcurrent
condition, the MOSFET switch’s internal resistance causes
the MOSFET’s output voltage to drop at the OVL[1:4] pin. If
the MOSFET’s output voltage drops to less than the volt-
age at the VREF voltage reference pin, the AT43311 inter-
prets this drop as an overcurrent condition. The AT43311
does internal filtering to make sure that spurious or switch-
ing transients are ignored. If an overcurrent condition
exists, the AT43311 removes the power from that port by
de-activating the port’s PWR[1:4] pin and reports the condi-
tion to the Host.
Status Change Register
Bit Function
0
Hub status change
1
Port1 status change
2
Port2 status change
3
Port3 status change
4
Port4 status change
5-7 Reserved
Value
0
1
0
1
0
1
0
1
0
1
0
Meaning
No change in status
Change in status detected
No change in status
Change in status detected
No change in status
Change in status detected
No change in status
Change in status detected
No change in status
Change in status detected
Default values
5
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