M38B53M4-059FP datasheet(262/355 Pages) MITSUBISHI

262 / 355 page

3-14

APPENDIX

38B5 Group User’s Manual

3.3 Notes on use

3.3.1 Notes on interrupts

(1)

Switching external interrupt detection edge

For the products able to switch the external interrupt detection edge, switch it as 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)

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. 3.3.2 Sequence of check of interrupt request bit

Fig. 3.3.1 Sequence of switch 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.

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.

M38B53M4-059FP Datasheet(PDF) 262 Page - Mitsubishi Electric Semiconductor