M66591GP_15 datasheet(77/135 Pages) RENESAS

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M66591GP

Rev .1.00 Nov . 30, 2004 page 75 of 131

3.2 M66591 Initial Setting and Clock Control

This chapter explains the method of initial setting, the detection method of attach/detach to the host, and the

execution method of clock control and remote wakeup in suspend/resume concerning M66591.

3.2.1

M66591 Initial Setting

In initial setting process of the M66591, USB operation is enabled and input of the VBUS pin is confirmed by

polling the VBUSSTS bit of Interrupt Status Register 0. According to the input status of the VBUS pin, either the

VBUS interrupt waiting process or the USB attach processing is executed.

If VBUSSTS bit is “0”, M66591 is not connected to the host, enable the VBUS interrupt and wait for connection to

the host.

If VBUSSTS bit is “1”, M66591 is already connected to the host before initial setting, execute attach processing.

The detailed process flowchart is shown in Figure 3.3.

Further, as the VBUS pin is directly input from the VBUS pin of the USB connector, chattering removal process by

software is required for confirmation of the input status.

Waiting for VBUS

interrupt

Clearing all registers

Confirm VBUSSTS

status.

USB attach

processing

USB Initial

VBUSSTS='1'

in connecting

VBUSSTS='0'

in not connecting

Clear all necessary registers of the M66591.

Enable USB operation.

Confirm the connect status after hardware reset by

polling VBUS pin. It is necessary to filter chattering when

polling VBUS pin.

As it is already connected to a PC as a result of the polling

of the VBUS pin, execute USB attach processing.

As it is not connected to a PC as a result of the polling of

the VBUS pin, enable the VBUS interrupt then wait for

connection.

Setting XTAL

Enable clock of the M66591 according to the oscillator

used for the system.

All the necessary interrupts are enabled.

Enabling necessary

interrupt

Enabling USB

operation

(USBE='1')

Figure 3.3 M66591 Initial Setting Process Flowchart

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