7643 datasheet(249/424 Pages) RENESAS

249 / 424 page

Rev.2.00

Aug 28, 2006

page 128 of 202

7643 Group

REJ09B0133-0200

APPLICATION

2.6 USB

Fig. 2.6.23 Frequency synthesizer connection and setting of division ratios

f(XIN)

24MHz

FSM1

FSD

48MHz

1/1

1/2

Invalid

FSM2

FSM1 : Frequency synthesizer multiply register 1

FSM2 : Frequency synthesizer multiply register 2

FSD : Frequency synthesizer divide register

(FF16)(0016)

fPIN

fVCO

fUSB

(25516)

fSYN

2.6.7 Application example

The following are several 7643 Group application examples showing the control procedure for performing

USB controls.

(1)

Application example 1: Initialization of USB function control unit

Outline: Initialization the USB function control unit (USB FCU) is performed.

Specification: - To generate the 48MHz required for fUSB, the frequency synthesizer is used.

- USB FCU is enabled.

- Each endpoint is initialized.

Endpoint 0: Control transfer

Endpoint 1: Bulk transfer

Endpoint 2: Bulk transfer

This is an example when the MCU is operating at Vcc = 5V.

The following settings are required when using Vcc = 3V.

q Set the USB line driver supply enable bit (USB control register, bit 4) to “0” to disable the DC-

DC converter.

q Set

φ to 6MHz or less.

When f(XIN) = 24MHz, clear bit 7 of the clock control register (XIN divider select bit) to “0”.

Figure 2.6.23 shows the division settings of the frequency synthesizer, Figures 2.6.24 to 2.6.26

show related register settings, and Figures 2.6.27 to 2.6.29 show control procedure examples.

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