Figure 15.7 Usb Cable Disconnection (When Usb Module Stop Or Software Standby Is Used) - Hitachi H8S/2215 Series Hardware Manual

(4) USB Cable Disconnection (When USB module stop or software standby is used)
If the USB cable enters the disconnection state from the connection state in an application (self
powered) where USB module stop or software standby mode is used, perform the operation
shown in figure 15.7.
USB function
Disconnect the USB cable
Start USB operating
clock oscillation
USB clock stabilization
time has passed?
A USB operating clock
oscillation detection
interrupt occurs
Stop SOF marker function
Stop UDC core
Notes:
*1 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
specified as both edge sensitive. When
*2 Before entering the software standby state, USB module operation must be stopped by setting the MSTPB0 bit of
MSTPCRB register to 1.
Figure 15.7 USB Cable Disconnection (When USB Module Stop or Software Standby is
Rev. 3.0, 10/02, page 488 of 686
External interrupt
*1
No
Yes
is used, a VBUS interrupt in the USB module need not to be used.
Firmware
*1
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 connections by using
the port function of
SOF marker
function enabled?
Yes
Stop SOF marker fouction
Clear SFME of UCTLR to 0
Reset UDC core
Set UDCRST of UCTRL to 1.
Enable D+ pull up
by the port
Does system
enter power-down
mode?
Yes
Stop USB module
Set MSTPB0 of MSTPCRB to 1
Enter software standby
(only if necessary)
Wait for USB
cable connection
. In this case, the
Used)
No
Check the USB cable
disconnection state
No
No
*2
*2
pin must be