Renesas Single-Chip Microcomputer M37531T-ADS Technické informace stáhnout pdf (Strana 35)

MESC TECHNICAL NEWS

No.M16C-25-9905

( 1 / 2 )

GRADE

M16C/60 , M16C/20 Series

Precautions for Wait and Stop modes

1. Related devices

M16C/60 Series , M16C/20 Series

2. Precautions

The M16C has both WAIT and STOP modes. These modes can be used to reduce power

consumption when the CPU is not required to perform any work. To return to normal operating

mode after issuing a WAIT instruction or setting the all clock stop control bit, perform a hardware

reset or use an interrupt. The interrupts for canceling the WAIT and STOP modes must be

enabled before entering either mode. The priority level of the interrupts not used for these

modes should be set to 0 before switching into the WAIT or STOP modes. Also, if only hardware

______

reset or NMI interrupts are used for canceling the WAIT or STOP modes, all interrupt priority

level should be set to 0 before switching into the WAIT or STOP mode.

3. Examples

3.1 Use the following algorithm to enter the WAIT or STOP modes when an interrupt is

used to cancel either mode.

______ _______

• Hardware reset, NMI interrupt, and INT0 interrupt is used to cancel either mode

; Disable interrupt

; Enable interrupt

WAIT instruction or all clock stop control bit set

Insert 4 NOP instructions

; Enable INT0 interrupt

(In case of processor interrupt priority level=0)

; Disable all other interrupts

; Prevention of irregular interrupts issue.

See TECHNICAL NEWS No.M16C-14-9805

Set the interrupt enable flag (I flag) to “0”

Change the interrupt priority level to 1 or higher

Change all other interrupt priority levels to 0

Set the interrupt enable flag (I flag) to “1”

Insert 4 NOP instructions

; NOP instructions are required because M16C instruction queue reads forward 4

bytes from wait or stop instruction when program is stopped.

; Set the bit 0 of protect register to “1” before set the all clock stop control bit to “1” .

Related to M16C/60, M16C/20 series devices.

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Renesas Single-Chip Microcomputer M37531T-ADS Technické informace Strana 35