M38197 データシートの表示（PDF） - MITSUBISHI ELECTRIC

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M38197

SINGLE-CHIP 8-BIT MICROCOMPUTER

MITSUBISHI ELECTRIC  

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

43

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