HD6417660 RENESAS [Renesas Technology Corp], HD6417660 Datasheet - Page 643

• Manufacturer Part Number: HD6417660
• Description: Renesas 32-Bit RISC Microcomputer
• Manufacturer: RENESAS [Renesas Technology Corp]

20.7
D+ Pull-Up Control: In a system where it is wished to disable USB host/hub connection
notification (D+ pull-up) (during high-priority processing or initialization processing, for
example), D+ pull-up should be controlled using a general output port. However, if a USB cable is
already connected to the host/hub and D+ pull-up is prohibited, D+ and D– will both go low (both
of D+ and D– pulled down on the host/hub side) and the USB function controller will mistakenly
identify this as reception of a USB bus reset from the host. Therefore, the D+ pull-up control
signal and USB_VBUS pin input signal should be controlled using an UPLUP output port and the
USB cable VBUS (AND circuit) as shown in the circuit example below (The UDC core in this
LSI maintains the powered state when the USB_VBUS pin is low, regardless of the D+/D– state.)
Detection of USB Cable Connection/Disconnection: As USB states, etc., 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 function (system installed in this LSI) power is off, a
voltage (5 V) will be applied from the USB host/hub. Therefore, an IC (such as an
HD74LV1G08A or 2G08A) that allows voltage application when the system power is off should
be connected externally.
48 MHz
Example of External Circuitry for USB Function Controller
Note: This example is for reference only, therefore proper operation is not guaranteed with this circuit example.
Figure 20.19 Example of USB Function Module External Circuitry
If system countermeasures are required for external surges and ESD noise, use a protective diode,
a noise canceller, etc.
This LSI
UCLK
USB function
controller
USB_VBUS
USB_PULLUP
USB_P
USB_N
IC allowing voltage application
when system power is off
(HD74LV1G126A, etc.)
IC allowing voltage application
when system power is off
(HD74LV1G(2G)08A, etc.)
Rev. 1.00, 02/04, page 605 of 804
USB cable
USB
connector
VBUS
GND
D+
D−