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M30245 Group
(2) USB Suspend Function
In the M30245 group, the USB suspend status flag (SUSPEND) of USB power management register
(address 0282
detected any bus activity on the D+/D- line for at least 3ms). Simultaneously, the USB suspend inter-
rupt request occurs.
To shift into the USB suspend state, control the USB function control unit in the following procedure.
Further, for changes in frequency synthesizer control register (address 03DC
trol register1 (address 0007
required.
USB Suspend Mode Control
1: Set USB clock enable bit of USB control register to "0". Do not write to USB internal registers (other
than the USBC, USBAD, and frequency synthesizer related registers) when the USB clock has
been disabled in the suspend state.
2: During the bus power supply operation as a low-power device, control it to reduce the total driving
current to 500µA or below (or 2.5mA or below when remote wakeup has been enabled as a high-
power device by the host CPU). For details of the power control in suspend, refer to USB2.0
specification.
3: Set frequency synthesizer enable bit of frequency synthesizer control register to "0".
4: Set the return interrupt from the USB suspend state. Set USB resume interrupt control register
(address 0058
peripheral functions used in remote wakeup.)
5: Set I flag to "1".
6: Stop the system clock by setting all clock stop control bit (bit 0 of CM1) to 1.
7: During the bus power supply operation, after setting the low-power consumption mode by dis-
abling interrupts that are not used in return from the USB suspend state, etc., execute the low-
power consumption mode.
Note: When the device is in self-powered operation, the above control is not required.
Rev.2.00 Oct 16, 2006
REJ09B0340-0200
) is set to "1" when the suspend signal has been received from the host CPU (or not
16
), clearing the corresponding bit of protect register (address 000A
16
). (When remote wakeup has been enabled, enable interrupt control register of the
16
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2. USB function
) or system clock con-
16
) is
16
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