H8SSLASH2218 datasheet(552/750 Pages) RENESAS

552 / 750 page

Section 14 Universal Serial Bus (USB)

Rev.6.00 Jun. 03, 2008 Page 504 of 698

REJ09B0074-0600

(3) Suspend and Remote-Wakeup Operations

Figures 14.9 and 14.10 are flowcharts of the suspend and remote-wakeup operations. If the

USB bus enters a non-suspend state from the suspend state due to a remote-wakeup signal from

this function, perform the operations shown below.

USB function

Firmware

USB cable connected

A bus idle of 3 ms or

more occurs

A suspend/resume

interrupt occurs

Suspend state

Output resume signal

to USB bus

A suspend/resume

interrupt occurs

Enable SPRSi and

IRQ6 interrupts

(Set SPRSiE in UIER3 to 1)

(Set IRQ6E in IER to 1)

Initialize standby

enable flag

(Clear standby enable

flag to 0)

Run user program

In one of the power-down

modes

Mask all interrupts

(Manipulate bit I using

LDC instruction, etc.)

Enable IRQ6 interrupt

(Set IRQ6E in IER to 1)

Unmask all interrupts

(Clear bit I using LDC

instruction, etc.)

Transition to one

of the power-down modes

(Execute SLEEP

instruction)

Suspend interrupt

processing

(see figure 14.8)

IRQ6

NMI or

IRQx

IRQ6

Suspend/remote-wakeup

interrupt processing

Main process

Yes

Standby enable

flag = 0?

Remote-wakeup

interrupt processing

(see figure 14.10)

Standby enable

flag = 1?

Notes: 1. The standby enable flag is a software flag for controlling transition to the standby

state (one of the power-down modes). There is no such hardware flag.

2. Interrupts should be masked from when the

IRQ6 interrupt is received until the

SLEEP instruction is executed. Finally, unmask the interrupts using the LDC

instruction or the like and execute the SLEEP instruction immediately afterward.

Remote-

wakeup

Figure 14.9 Example Flowchart of Suspend and Remote-Wakeup Operations

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