Datasheet

Section 16 USB Function Module (USB)
R01UH0309EJ0500 Rev. 5.00 Page 1015 of 1408
Sep 24, 2012
H8S/2456, H8S/2456R, H8S/2454 Group
16.9 Example of USB External Circuitry
1. USB Transceiver
This module supports the on-chip transceiver only, not the external transceiver.
2. D+ Pull-Up Control
The general output port (P20) is used for D+ pull-up control pin. The P20 pin is driven high by
the PULLUP_E bit of CTLR when the USB cable VBUS is connected.
Thus, USB host/hub connection notification (D+ pill-up) is enabled.
3. 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 installing 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.
Vcc
Regulator*
1
Vcc
(3.3 V)
VBUS
(5 V)
1.5 kΩ
Vcc
(3.3 V)
DrVCC
(3.3 V)
USD+
D+
VBUS*
3
P20
Notes:
1.
2.
3.
Vcc
*
2
USD- DrVSS Vss
GND
D-
USB connector
On-chip transceiver
External pull-up
control circuit
supporting full-speed
Reduce voltage to the operating voltage of this LSI (3.3 V).
To protect this LSI from being damaged, use the IC (such as HD74LV-A Series) which can
be applied voltage even when the system power is turned off.
Prevent noise from the VBUS pin while the USB is performing communication.
PULLUP_E
USB
Figure 16.23 Example of Circuitry in Bus Power Mode