Detecting Connection And Disconnection - Fujitsu MB90335 Series Hardware Manual

MB90335 Series
11.4.1

Detecting Connection and Disconnection

This section describes how to detect connection to and disconnection from the USB
host.
■ Example USB System Connection
Connection to and disconnection from the USB host can be detected by connecting an external interrupt pin
to the VBUS pin on the USB connector and connecting a pull-down resistor. Figure 11.4-3 shows an
example connection for the D+, D-, and VBUS pins on the USB connector.
USB host
●
Detecting connection
VBUS
Enable external interrupts
ENx
ERx
{LBx,LAx}
HCON
The device uses the following sequence to detect a connection with the host PC.
1. Set the external interrupt connected to the VBUS to detect "H" level inputs and enable the interrupt.
2. Detection of an "H" level on the external interrupt pin indicates a connection to a USB host. When this
occurs, wait for the VBUS to stabilize.
CM44-10137-6E
Figure 11.4-3 Example USB System Connection
B connector
VBUS
D+
D-
Figure 11.4-4 Operation When Detecting a Connection
Connection to HOST
{0,1}
Time for VBUS to stabilize
FUJITSU MICROELECTRONICS LIMITED
11.4 Operation Explanation of USB Function
USB device
VBUS(5V)
(3.3V)
27Ω
1.5kΩ
27Ω
Enable connection
CHAPTER 11 USB FUNCTION
This device
External interrupt
HCON
D+
D-
Change in interrupt level
{0,0}
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