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(2) USB Cable Connection (When USB module stop or software standby is used)
If the USB cable enters the connection state from disconnection state an application (self
powered) where USB module stop or software standby mode is used, perform the operation as
shown in figure 15.5.
USB function
Connect the USB cable
Start USB operating
clock oscillation
USB clock stabilization
time has passed?
Yes
A USB operating clock
oscillation detection
interrupt occurs
Automatically load
EPINFO to the UDC core
Complete USB
module initialization
Receive bus reset
A bus reset interrupt occurs
Note:
*
A VBUS interrupt in the USB module cannot be detected in the software standby state or in the USB
module stop state. Accordingly, in an application in which software standby or USB module stop is used
in self-powered mode, a VBUS interrupt of the USB must be detected via the external interrupt pin
In this case, the
in the USB module need not to be used.
Figure 15.5 USB Cable Connection (When USB Module Stop or Software Standby is Used)
Rev. 3.0, 10/02, page 486 of 686
External interrupt
*
No
pin must be specified as both-edge sensitive. When
Firmware
*
Yes
Software
standby?
No
USB module
stopped?
Yes
Cancel USB module stop mode
Clear MSTPB0 of MSTPCRB to 0
Wait for USB operating clock
stabilization
Clear CK48READY of UIFR3
Check by using
the port function of
Clear all FIFOS
System ready?
Yes
Enable D+ pull up by
the port
Cancel UDC core reset
(Clear UDCRST of UCTLR to 0)
Initializa the firmware
Wait for a setup interrupt
is used, a VBUS interrupt
No
Check the USB cable
connection state
No
.
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