Renesas SH7641 - Manual (Page 839)

Section 20 USB Function Module
Rev. 4.00 Sep. 14, 2005 Page 789 of 982
REJ09B0023-0400
20.9 USB Bus Power Control Method
20.9.1 USB Bus Power Control Operation
This LSI can operate using a USB bus power control method.
The following describes notes on the LSI using the USB bus power control method.
Changing to High-Power Function: According to the USB standard, the startup operation (from
connecting cables to completing enumeration) is handled as a low-power function. Changing to
the high-power function can be checked by detecting reception of a SET_CONFIGURATION
request from USBIFR2 and IFRIER2/SETC and confirming USBIFR2/CFGV = 1.
Suspending: In this LSI, an interrupt by detecting the USB suspend signal or awake signal can be
shared with an
IRQ0 or IRQ1 interrupt by specifying USBCTRL/SUSPEND = 1. (See
figure 20.19.)
This causes an
IRQ1 interrupt to occur by specifying USBIFR2/SUSPS = 1 to change the LSI
state to the standby mode. An
IRQ0 interrupt occurs by specifying USBIFR2/AWAKE=1, the LSI
can be returned from the standby mode. Since the LSI must enter the USB suspend state within 10
ms after the USB suspend signal is detected, an
IRQ1 interrupt must be set to be processed prior to
other interrupts. When the
IRQ0 interrupt priority is lower than the interrupt request mask level
(SR/I[3:0]), the LSI cannot be returned from the suspend state. Make sure that the
IRQ0 interrupt
priority is higher than the interrupt request mask level (SR/I[3:0]). Figure 20.20 shows the
operation timing.