AT43310 データシートの表示（PDF） - Atmel Corporation
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AT43310 Datasheet PDF : 25 Pages
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AT43310
Endpoint0
Endpoint0 is the AT43310’s default endpoint used for enu-
meration of the Hub and exchange of configuration infor-
mation and requests between the Host and the AT43310.
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 AT43310 has been enumerated and configured by the
Host through Endpoint0.
Power Management
A hub is allowed to draw up to 500 mA from the host or
upstream hub. The AT43310’s itself and its external circuit
except for the downstream ports consume less than 100
mA. Therefore 100 mA is available for each of the hub’s
downstream devices. The power supplied to each port is
individually monitored and controlled by AT43310.
The USB specifications requires that the voltage drop at
the power switch be no more than 100 mV. Careful design
and selection of the power switch is required to meet this
specifications. This is best achieved by using a MOSFET
switch with a very low on resistance. If the port power are
switched individuallly, this resistance must be 1Ω or less
under the worst case condition to assure that even if a
downstream device dissipates 100mA the drop across the
switch is less than 100 mV. If the downstream devices are
switched in common, the switch resistance must be no
more than 250mΩ.
A suitable MOSFET switch for a AT43310 based hub is a P
channel enhancement 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 OVLx# pin.
Whenever an overcurrent condition occurs, the MOSFET
switch’s internal resistance causes the output voltage to
drop. If the MOSFET’s output voltage drops to less than the
voltage at the VREF voltage reference pin, the AT43310
interpretes this as an overcurrent condition. The AT43310
does internal filtering to make sure that spurious or switch-
ing transients are ignored. If a true overcurrent condition
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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