H8SSLASH2218 datasheet(550/750 Pages) RENESAS

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Section 14 Universal Serial Bus (USB)

Rev.6.00 Jun. 03, 2008 Page 502 of 698

REJ09B0074-0600

14.5.3

Suspend and Resume Operations

(1) Suspend and Resume Operations

Figures 14.7 and 14.8 are flowcharts of the suspend and resume operations. If the USB bus

enters the suspend state from a non-suspend state, or if it enters a non-suspend state from the

suspend state due to a resume signal from up-stream, 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

A resume interrupt is

generated from up-stream

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

Suspend/resume interrupt

processing

Main process

Yes

Standby enable

flag = 0?

Resume interrupt

processing

(see figure 14.8)

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.

Figure 14.7 Example Flowchart of Suspend and Resume Operations

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