M38197MA Datasheet, PDF (44/60 Pages) Mitsubishi Electric Semiconductor – SINGLE-CHIP 8-BIT CMOS MICROCOMPUTER

MITSUBISHI MICROCOMPUTERS
3819 Group
SINGLE-CHIP 8-BIT CMOS MICROCOMPUTER
NOISE FILTER
The noise filter uses a sampling clock to remove the noise compo-
nent digitally from the input signal of P45/INT1/ZCR pin. The
sampling clock can be selected from 8 µs, 16 µs, or 32 µs (at
f(XIN)= 8.38 MHz) and this is used to change the noise component
to be removed. It is also possible to generate an internal trigger
and INT1/ZCR interrupt request directly without passing through
the noise filter. When passing through the noise filter, either both-
sided edge detection or one-sided edge detection can be selected
as the interrupt request generating source. The zero cross detec-
tion control register is used for this selection. Furthermore, switch
between rising edge and falling edge is performed with the bit 1 of
the interrupt edge selection register (address 003A16).
Input signal from
P45/INT1/ZCR pin
Sampling clock
RESET
DQ
C
R
A _{D QB}
C
R
Fig. JE-4 Noise filter circuit diagram
S QC
R
DQ
C
R
One-sided/both-sided edge
detection selection bit
(bit 4 of ZCRCON)
“0”
INT1/ZCR
“1”
interrupt request
RESET
Sampling clock
P45/INT1/ZCR
Input signal from
P45/INT1/ZCR pin
A
B
C
INT1/ZCR
(one-sided edge)
interrupt request _{(both-sided edge)}
Fig. JE-5 Timing of noise filter circuit
0V
(Note 1)
(Note 2)
Switched with
bit 4 of ZCRCON
Notes 1 : Ignored this because of treating this as noise
2 : INT1/ZCR interrupt request occurs
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