M30201 datasheet(45/172 Pages) RENESAS

45 / 172 page

Mitsubishi microcomputers

M30201 Group

SINGLE-CHIP 16-BIT CMOS MICROCOMPUTER

Interrupts

Precautions for Interrupts

(1) Reading address 0000016

• When maskable interrupt is occurred, CPU read the interrupt information (the interrupt number and

interrupt request level) in the interrupt sequence.

The interrupt request bit of the certain interrupt written in address 0000016 will then be set to “0”.

Reading address 0000016 by software sets enabled highest priority interrupt source request bit to “0”.

Though the interrupt is generated, the interrupt routine may not be executed.

Do not read address 0000016 by software.

(2) Setting the stack pointer

• The value of the stack pointer immediately after reset is initialized to 000016. Accepting an interrupt

before setting a value in the stack pointer may become a factor of runaway. Be sure to set a value in the

stack pointer before accepting an interrupt. Concerning the first instruction immediately after reset,

generating any interrupts is prohibited.

(3) External interrupt

________

• Either an “L” level or an “H” level of at least 250 ns width is necessary for the signal input to pins INT0

________

and INT1 regardless of the CPU operation clock.

________

• When changing a polarity of pins INT0 and INT1, the interrupt request bit may become "1". Clear the

______

interrupt request bit after changing the polarity. Figure 1.33 shows the switching condition of INT inter-

rupt request.

______

Figure 1.33. Switching condition of INT interrupt request

(4) Changing interrupt control register

See "Changing Interrupt Control Register".

Set the interrupt priority level to level 0

(Disable INTi interrupt)

Set the polarity select bit

Clear the interrupt request bit to “0”

Set the interrupt priority level to level 1 to 7

(Enable the accepting of INTi interrupt request)

Clear the interrupt enable flag to “0”

(Disable interrupt)

Set the interrupt enable flag to “1”

(Enable interrupt)

M30201 Datasheet(PDF) 45 Page - Renesas Technology Corp