131

CHAPTER 6. INTERRUPT FUNCTIONS

Fig. 6-4 INT0 Noise Elimination Circuit Input/Output Timing

Remarks tSMP = tCY or 64/fXX

Specification of the detected edge of the INT0 input and selection of the sampling clock is performed by the edge

detection mode register (IM0).

As signals are also input via the noise elimination circuit when the INT0 pin inputs data as a port, the input data

must be of sufficient width to avoid being eliminated as noise.

INT2 functions as an externally testable input which sets a testable flag on detection of a rising edge. Noise

elimination by the sampling clock is not performed, but as there is a function for eliminating pulses which are

narrower than the analog delay, a signal of adequate width must be input as in the case of INT0 (see Fig. 6-5).

Fig. 6-5 INT2 Input Noise Elimination

Analog
Delay
Analog
Delay
INT2 Input
Eliminated
as Noise
INT2 Input
Received
Eliminated as Noise
H H
L L
L L
H H
L L
L
H
L L
Eliminated as Noise
t
SMP
t
SMP
t
SMP
t
SMP
t
SMP
➀➁➂
Sampling Cycle
(t
SMP
) or Less
INT0
Sheped
Output
1 to 2 Times t
SMP
INT0
Sheped
Output
(a)
2 or More Times 
t
SMP
INT0
Sheped
Output
INT0
Sheped
Output
(b)