Renesas HD6417641 用户手册
Section 20 USB Function Module
Rev. 4.00 Sep. 14, 2005 Page 786 of 982
REJ09B0023-0400
20.8
Example of USB External Circuitry
USB Transceiver: When an on-chip transceiver is not used, a USB transceiver IC (such as a
PDIUSBP11) must be connected externally. The USB transceiver manufacturer should be
consulted concerning the recommended circuit from the USB transceiver to the USB
connector, etc.
PDIUSBP11) must be connected externally. The USB transceiver manufacturer should be
consulted concerning the recommended circuit from the USB transceiver to the USB
connector, etc.
D+ Pull-Up Control: In a system where it is wished to delay USB host/hub connection
notification (D+ pull-up) (during high-priority processing or initialization processing, for
example), D+ pull-up is controlled using a general output port. When the USB cable has been
connected to the host or hub and D+ pull-up is inhibited, D+ and D- are placed in the low level
state (D+ and D- are pull down on the host or hub side) and the USB module recognizes as if the
USB bus reset has been received from the host. In that case, the D+ pull-up control signal and
VBUS pin input signal should be controlled using a general output port and the USB cable VBUS
(AND circuit) as shown in figure 20.17. (The UDC core of this LSI holds the powered state
independent of D+ and D- state when the VBUS pin is low level.)
notification (D+ pull-up) (during high-priority processing or initialization processing, for
example), D+ pull-up is controlled using a general output port. When the USB cable has been
connected to the host or hub and D+ pull-up is inhibited, D+ and D- are placed in the low level
state (D+ and D- are pull down on the host or hub side) and the USB module recognizes as if the
USB bus reset has been received from the host. In that case, the D+ pull-up control signal and
VBUS pin input signal should be controlled using a general output port and the USB cable VBUS
(AND circuit) as shown in figure 20.17. (The UDC core of this LSI holds the powered state
independent of D+ and D- state when the VBUS pin is low level.)
Detection of USB Cable Connection/Disconnection: As USB states are managed by hardware in
this module, a VBUS signal that recognizes connection/disconnection is necessary. The power
supply signal (VBUS) in the USB cable is used for this purpose. However, if the cable is
connected to the USB host/hub when the on-chip function LSI power is off, a voltage (5 V) will be
applied from the USB host/hub. Therefore, an IC (HD74LV1G08A, 2G08A, etc.) that allows
voltage application when the system power is off should be connected externally.
this module, a VBUS signal that recognizes connection/disconnection is necessary. The power
supply signal (VBUS) in the USB cable is used for this purpose. However, if the cable is
connected to the USB host/hub when the on-chip function LSI power is off, a voltage (5 V) will be
applied from the USB host/hub. Therefore, an IC (HD74LV1G08A, 2G08A, etc.) that allows
voltage application when the system power is off should be connected externally.