M16CSLASH1N datasheet(217/238 Pages) RENESAS

217 / 238 page

Rev.1.00

Oct 20, 2004

page 205 of 222

M16C/1N Group

REJ090007-0100Z

20. Precautionary Notes in Using the Device

Example 1. When an interrupt is used to cancel wait mode

When canceling wait mode by a hardware reset and an INT0 interrupt.

Set the interrupt enable flag (I flag) to "0"

Change the INT0 interrupt priority level to 1 or higher

Change all other interrupt priority level to 0

Insert 4 NOPs instructions

Set the interrupt enable flag (I flag) to "1"

WAIT instruction

Insert 4 NOPs instructions

; Disable interrupt

; Enable INT0 interrupt

In case of processor interrupt priority level = 0

; Disable all other interrupts

; Prevent irregular interrupt occurring

; Enable interrupts

Example 2. When only hardware reset is used to cancel wait mode

Set the interrupt enable flag (I flag) to "0"

Change all interrupt priority level to 0

WAIT instruction

Insert 4 NOPs instructions

; Disable interrupt

; Disable maskable interrupt

; Put at least 4 NOPs after a wait instruction because

when switching to a wait mode, 4 instructions are

prefetched after the wait instruction.

; Put at least 4 NOPs after a wait instruction because

when switching to a wait mode, 4 instructions are

prefetched after the wait instruction.

20.1.3 Stop and Wait Modes

____________

When returning from a stop mode by hardware reset, RESET pin must be "L" level until the main-

clock has stabilized.

2. When switching to a stop or wait mode, 4 instructions are prefetched after the stop or wait instruc-

tion. And so, ensure that at least 4 NOPs follow the stop (the all-clock stop bit to "1") or wait

instruction.

3. A Stop or wait mode is cancelled by a hardware reset or an interrupt. If an interrupt is to be used to

cancel a stop or wait mode, that interrupt must first have been enabled, and the priority level of the

interrupt which is not used to cancel must have been changed to 0 before shifting to either mode.

If only a hardware reset is used to cancel a stop or wait mode, change the priority level of all

interrupt to 0, then shift to either mode.

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