7220 Datasheet, PDF (225/303 Pages) Renesas Technology Corp – 8-BIT SINGLE-CHIP MICROCOMPUTER

APPENDIX
6.3 Notes on use
(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.
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. 6.3.6 Sequence for switching an external
interrupt detection edge
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.
Clear the serial I/O interrupt enable bit to “0”
(interrupt disabled)
Select the serial I/O mode
(set the serial I/O port selection bit to “1”)
NOP (one or more instructions)
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)
Fig. 6.3.7 Initialization for serial I/O
6-6
7220 Group User’s Manual