HD6417641 RENESAS [Renesas Technology Corp], HD6417641 Datasheet - Page 836

• Manufacturer Part Number: HD6417641
• Manufacturer: RENESAS [Renesas Technology Corp]

Section 20 USB Function Module
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.
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.)
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.
Rev. 4.00 Sep. 14, 2005 Page 786 of 982
REJ09B0023-0400