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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.
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.
6-6
Clear an interrupt enable bit to "0" (interrupt disabled)
Set the interrupt request bit to "1" (interrupt enabled)
Fig. 6.3.6 Sequence for switching an external
Clear the serial I/O interrupt enable bit to "0"
(set the serial I/O port selection bit to "1")
Clear the serial I/O interrupt request bit to "0"
Set the serial I/O interrupt enable bit to "1"
Fig. 6.3.7 Initialization for serial I/O
7220 Group User's Manual
Switch the detection edge
Clear an interrupt request bit to "0"
(no interrupt request issued)
interrupt detection edge
(interrupt disabled)
Select the serial I/O mode
NOP (one or more instructions)
(no interrupt request issued)
(interrupt enabled)
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