Renesas CPU Board M3A-HS19 Manual de usuario descargar pdf (Pagina 4)

SH7285/SH7286 USB Function Module

USB to Serial Conversion Application Note

2.3 Detecting a Connection to the USB Host

A connection to the USB host is detected using the cable connect interrupt (the BRST bit in the USBIFR0 register).

The cable connect interrupt occurs when a USB device cable is connected to the USB host.

After the user configures the MCU, the sample program pulls up the USB data bus D+ pin using the general output

port. The USB host recognizes that a USB device is connected by the pull-up.

Figure 2.1 shows an operation flowchart

of the sample program, and

Figure 2.2 shows the USB Function Module Peripheral Block Circuit.

Yes

Connects a cable

USB Function (Hardware) Sample Program (Software)

Cable is not connected

VBUS = 0

UDC core is reset

USB cable is connected

Pulls up D+ pin

Releases the UDC core reset

Receives bus reset

USBIFR0/BRSY = 1

Bus reset interrupt

Waits for receiving

the setup command

Clears buffer in software

Clears the bus reset flag

USBIFR0/BRSY = 0

Clears all buffers

ActBusReset

Configures the MCU

Initializes the memory

Initializes the USB module

Main loop

USBIFR0/BRST interrupt

Sets CPG

Sets BSC

Sets I/O PORT

Sets PFC

USBPND pin (PB10)

Sets clock in the

USB module

Sets the interrupt level

SetUsbModule

Pull-up enabled

D+ pin (PB10)

High

Interrupt started

Interrupt completed

Main processing started

InitMemory

InitSystem

Figure 2.1 Detecting a Connection to the USB Host

REJ05B1152-0100/Rev.1.00 May 2008 Page 4 of 35

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