m5m51016btp Renesas Electronics Corporation., m5m51016btp Datasheet - Page 158

• Manufacturer Part Number: m5m51016btp
• Description: Renesas 16-bit Single-chip Microcomputer M16c Family / M16c/20 Series
• Manufacturer: Renesas Electronics Corporation.

M30245 Group
Rev.2.00 Oct 16, 2006
REJ09B0340-0200
(3) Disable of USB Function Control Unit
(4) Vbus Detection
After the USB function control unit being enabled, if the system design requires to disable the USB
function, follow the procedure below:
Normally, for system design which continues enabling the USB function, disabling the USB function
control unit is not required.
During USB self-powered operation, the Vbus detect function is used to switch into bus power only
when the device is connected to the host PC and power supply is available from the Vbus, for minimiz-
ing battery consumption. To use the Vbus detect function, it is necessary that the VbusDTCT pin is
processed by hardware and the Vbus detect interrupt is set by software. The VbusDTCT pin is used
for the Vbus detect function. When operating the USB in self-powered mode, connect the Vbus line
from the USB connector to the VbusDTCT pin. For enable/disable of the Vbus detect function, set
Vbus detect enable bit (bit 7 at address 001F
priority level by using USB Vbus detect interrupt control register (VBDIC: address 005C
the USB host powers ON/OFF, a Vbus detect interrupt will be occurred. When a Vbus detect interrupt
is occurred, the Vbus detect state bit located in the port 9 data register (bit 1 at address 03F1
be read to determine if the Vbus is powered ON/OFF.
To avoid receiving a false Vbus detect interrupt at start-up, the Vbus detect should be enabled before
enabling the Vbus detect interrupt. Use the following procedure when enabling the Vbus detect func-
tion:
1: Disable the USB clock by clearing USB enable bit (USBC7) to “0”.
2: Disable the USB clock by clearing USB clock enable bit (USBC5) to “0”.
3: Disable the frequency synthesizer by clearing frequency synthesizer enable bit (FSE) to “0”.
1: Enable a Vbus detect by setting “1” to Vbus detect enable bit (bit 7 at address 001F
2: Clear the Vbus detect interrupt request by setting “0” to Vbus detect interrupt request bit (bit 3 at
address 005C
3: Enable the Vbus detect interrupt by setting the Vbus detect interrupt priority level greater than
“000
2
” (bit 0 to 2 at address 005C
page 149 of 354
16
).
16
).
16
) of USB attach/detach register to “1”. Set the interrupt
2. USB function
16
16
). Each time
).
16
) should