Renesas M16C User Manual

Rev.1.10    Jul 01, 2005    page 287 of 318
REJ09B0124-0110

M16C/6N Group (M16C/6NK, M16C/6NM)

22. Usage Precaution

This document is under development and its contents are subject to change.

If the interrupt generate factor is changed, the IR bit of the interrupt control register for the changed

interrupt may inadvertently be set to “1” (interrupt requested). If you changed the interrupt generate factor

for an interrupt that needs to be used, be sure to set the IR bit for that interrupt to “0” (interrupt not

requested).

Changing the interrupt generate factor referred to here means any act of changing the source, polarity or

timing of the interrupt assigned to each software interrupt number. Therefore, if a mode change of any

peripheral function involves changing the generate factor, polarity or timing of an interrupt, be sure to set

the IR bit for that interrupt to “0” (interrupt not requested) after making such changes. Refer to the descrip-

tion of each peripheral function for details about the interrupts from peripheral functions.

Figure 22.3 shows the procedure for changing the interrupt generate factor.

• Either an “L” level of at least tW(INH) or an “H” level of at least tW(INL) width is necessary for the signal

________

________

input to pins INT0 to INT8 

(1)

 regardless of the CPU operation clock.

• If the POL bit in the INT0IC to INT8IC registers 

(2)

, the IFSR10 to IFSR15 bits in the IFSR1 register or the

IFSR23 to IFSR25 bits 

(3)

 in the IFSR2 register are changed, the IR bit may inadvertently set to “1”

(interrupt requested). Be sure to set the IR bit to “0” (interrupt not requested) after changing any of those
register bits.

NOTES:

1.

________

________

The pins INT6 to INT8 are only in the 128-pin version.

2. The INT6IC to INT8IC registers are only in the 128-pin version.
3. The IFSR23 to IFSR25 bits are effective only in the128-pin version. In the 100-pin version,

these bits are set to “0” (one edge).

Changing the interrupt source

Disable interrupt 

(2) (3)

Use the MOV instruction to set the IR bit to "0" 

(interrupt not requested) 

(3)

Change the interrupt 

generate factor

 

(including a mode change of peripheral function)

Enable interrupt 

(2) (3)

End of change

IR bit: A bit in the interrupt control register for the interrupt whose interrupt 

generate factor

 is

to be changed

NOTES:

1. The above settings must be executed individually. Do not execute two or more settings

simultaneously (using one instruction).

2. Use the I flag for the INTi interrupt (i = 0 to 8; 6 to 8 are only in the 128-pin version).

For the interrupts from peripheral functions other than the INTi interrupt, turn off the
peripheral function that is the source of the interrupt in order not to generate an interrupt
request before changing the interrupt 

generate factor

. In this case, if the maskable

interrupts can all be disabled without causing a problem, use the I flag. Otherwise, use
the corresponding ILVL2 to ILVL0 bit for the interrupt whose interrupt 

generate factor

 is

to be changed.

3. Refer to 22.7.6 

 for details about the instructions to

use and the notes to be taken for instruction execution.