3886 datasheet(139/380 Pages) RENESAS

139 / 380 page

2-22

3886 Group User’s Manual

APPLICATION

2.2 Interrupt

2.2.8 Notes on interrupts

(1)

Switching external interrupt detection edge

When switching the external interrupt detection edge, switch it in the following sequence.

Clear an interrupt enable bit to “0” (interrupt disabled)

↓

Switch the detection edge

↓

Clear an interrupt request bit to “0”

(no interrupt request issued)

↓

Set the interrupt enable bit to “1” (interrupt enabled)

Fig. 2.2.17 Sequence of switching detection edge

s Reason

The interrupt circuit recognizes the switching of the detection edge as the change of external input

signals. This may cause an unnecessary interrupt.

(2)

Check of interrupt request bit

q When executing the BBC or BBS instruction to an interrupt request bit of an interrupt request

more instructions before executing the BBC or BBS instruction.

Clear the interrupt request bit to “0” (no interrupt issued)

↓

NOP (one or more instructions)

↓

Execute the BBC or BBS instruction

Data transfer instruction:

LDM, LDA, STA, STX, and STY instructions

Fig. 2.2.18 Sequence of check of interrupt request bit

s Reason

If the BBC or BBS instruction is executed immediately after an interrupt request bit of an interrupt

request register is cleared to “0”, the value of the interrupt request bit before being cleared to “0”

is read.

3886 Datasheet(PDF) 139 Page - Renesas Technology Corp