M38197MA Datasheet, PDF (43/60 Pages) Mitsubishi Electric Semiconductor – SINGLE-CHIP 8-BIT CMOS MICROCOMPUTER

MITSUBISHI MICROCOMPUTERS
3819 Group
SINGLE-CHIP 8-BIT CMOS MICROCOMPUTER
ZERO CROSS DETECTION CIRCUIT
The zero cross detection circuit compares the voltage applied to
P45/INT1/ZCR pin and VSS. The result can be read from the zero
cross detection circuit input bit (bit 7) of the zero cross detection
control register. It is set to “1” when the input voltage is higher than
VSS and to “0” when it is lower than VSS. The input signal to P45/
INT1/ZCR pin can select to either pass through the zero cross de-
tection comparator or not to do.
When using 100 V AC as input signal, insert an external circuit be-
tween it and P45/INT1/ZCR pin. Set the input current limiting
resistors used in the external circuit to a value which satisfies the
absolute maximum rating of port P45.
100V AC
VCC
R1
R2
P45/INT1/ZCR
VSS
Fig. JE-1 External circuit example for zero cross detection
b7
b0
Zero cross detection control register
(ZCRCON : address 003916)
Zero cross detection ON/OFF selection bit
0 : Without passing through zero cross detection comparator
1 : Passing through zero cross detection comparator
Not used (returns “0” when read)
Noise filter sampling clock selection bits (INT1)
b3 b2
0 0 : Not use noise filter
0 1 : f(XIN)/64 or f(XCIN)/64
1 0 : f(XIN)/128 or f(XCIN)/128
1 1 : f(XIN)/256 or f(XCIN)/256
One-sided/both-sided edge detection selection bit
0 : One-sided edge detection
1 : Both-sided edge detection
Not used (return “0” when read)
Zero cross detection circuit input bit (read only)
0 : Less than 0 V
1 : 0 V or more
Fig. JE-2 Structure of zero cross detection control register
P45/INT1/ZCR
Zero cross detection
ON/OFF selection bit
“0”
Rising/falling
“1”
edge switch
Zero cross detection
circuit input bit
When not using
the filter
When using
the filter
Noise filter
INT1/ZCR
interrupt request
Zero cross detection comparator
One-sided/both-sided edge
detection selection bit
Noise filter sampling clock
selection bit
1/256
f(XCIN)
f(XIN)
1/641/28
Divider
Fig. JE-3 Block diagram of zero cross detection circuit
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