H838532H datasheet(103/508 Pages) RENESAS

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Section 3 Exception Handling

Rev. 1.00 May 30, 2008 Page 83 of 484

REJ09B0436-0100

3.4.3

Method for Clearing Interrupt Request Flags

Use the recommended method, given below when clearing the flags of interrupt request registers

(IRR1, IRR2, IWPR).

• Recommended method

Use a single instruction to clear flags. The bit control instruction and byte-size data transfer

instruction can be used. Two examples of program code for clearing IRRI1 (bit 1 of IRR1) are

given below.

BCLR

#1,

@IRR1:8

MOV.B R1L, @IRR1:8 (set the value of R1L to B'11111101)

• Example of a malfunction

When flags are cleared with multiple instructions, other flags might be cleared during

execution of the instructions, even though they are currently set, and this will cause a

malfunction.

Here is an example in which IRRI0 is cleared and disabled in the process of clearing IRRI1

(bit 1 of IRR1).

MOV.B @IRR1:8,R1L ......... IRRI0 = 0 at this time

AND.B #B'11111101,R1L ..... Here, IRRI0 = 1

MOV.B R1L,@IRR1:8 ......... IRRI0 is cleared to 0

In the above example, it is assumed that an IRQ0 interrupt is generated while the AND.B

instruction is executing.

The IRQ0 interrupt is disabled because, although the original objective is clearing IRRI1,

IRRI0 is also cleared.

H838532H 데이터시트(PDF) 103 Page - Renesas Technology Corp