H8SSLASH2218 datasheet(551/750 Pages) RENESAS

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Section 14 Universal Serial Bus (USB)

Rev.6.00 Jun. 03, 2008 Page 503 of 698

REJ09B0074-0600

(2) Suspend and Resume Interrupt Processing

Figure 14.8 is a flowchart of suspend and resume interrupt processing.

USB function

Firmware

Resume interrupt

processing

USB operating clock stabilization

detection interrupt processing

Suspend interrupt

processing

Start USB operating

clock oscillation

A USB operating clock

stabilization detection

interrupt occurs

Clear USB module

stop 2 mode

(Clear MSTPB0

in MSTPCRB to 0)

Clear resume flag

(Clear SPRSi in UIFR3

to 0)

Clear USB operating clock

stabilization detection flag

(Clear CK48READY

in UIFR3 to 0)

Resume main process

Prohibit IRQ6

(Clear IRQ6E in IER to 0)

Clear suspend flag

(Clear SPRSi in UIFR3

to 0)

Confirm that

remote-wakeup is

prohibited

Confirm that

remote-wakeup is enabled

Enable USB module

stop mode

(Set MSTPB0

in MSTPCRB to 1)

Set standby enable

flag to 1

Clear standby enable

flag to 0

Wait for USB operating

clock stabilization

Suspend

state confirmed?

(SPRSs in UIFR3 =

1?)

Suspend

state confirmed?

(SPRSs in UIFR3 =

1?)

Remote-

wakeup enabled?

(RWUPs in UDRR

= 1)

USB operating

clock stabilization time

has passed?

Yes

EXIRQx

Standby enable

flag = 0?

Suspend

state confirmed?

(SPRSs in UIFR3 =

1?)

IRQ6

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.

3. The remote-wakeup function cannot be used unless it is enabled by the host. Accordingly, the remote-wakeup function cannot be used

unless it is enabled by the host. Accordingly, make sure to check RWUPs in UDRR before using the remote-wakeup function. However, it is

not necessary to confirm that the remote-wakeup function is enabled by the host if the application does not make use of this function.

4. When resuming using the remote wakeup function, the USB module stop state must already be cleared.

5. Return to the main process and wait for the USB operating clock stabilization detection interrupt. When resuming by means of remote-

wakeup the USB operating clock has already stabilized, so this step is not necessary.

Enable IRQ6 interrupt

(Set IRQ6E in IER to 1)

Clear suspend flag

(Clear SPRSi in UIFR3

to 0)

Figure 14.8 Example Flowchart of Suspend and Resume Interrupt Processing

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