7220 datasheet(225/303 Pages) RENESAS

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APPENDIX

6.3 Notes on use

7220 Group User’s Manual

6-6

(2)

How to switch an external interrupt detection

edge

For the products able to switch the external

interrupt detection edge, switch it as Figure

6.3.6.

Reason

The interrupt circuit recognizes the switching

of the detection edge as the change of external

input signals. This may cause an unnecessary

interrupt.

6.3.4 Notes on serial I/O

(1)

Initialization for the serial I/O

For the serial I/O interrupt, initialize as Figure

6.3.7.

(2)

Write transmit data to transmit buffer

When an external clock is used as the

synchronous clock for the clock synchronous

serial I/O, write the transmit data to the serial

I/O shift register at HIGH of the transfer clock

input level.

Fig. 6.3.6

Sequence for switching an external

interrupt detection edge

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 request bit to “1” (interrupt enabled)

Fig. 6.3.7

Initialization for serial I/O

NOP (one or more instructions)

Clear the serial I/O interrupt enable bit to “0”

(interrupt disabled)

Clear the serial I/O interrupt request bit to “0”

(no interrupt request issued)

Set the serial I/O interrupt enable bit to “1”

(interrupt enabled)

Select the serial I/O mode

(set the serial I/O port selection bit to “1”)

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