M38B53M4-059FP datasheet(240/355 Pages) MITSUBISHI

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38B5 Group User’s Manual

APPLICATION

2.11 Clock generating circuit

2.11.2 Clock generating circuit application examples

(1)

Status transition during power failure

Outline: The clock is counted up every one second by using the timer interrupt during a power

failure.

Fig. 2.11.2 Connection diagram

Specifications: •Reducing power dissipation as low as possible while maintaining clock function

•Clock: f(XIN) = 4.19 MHz, f(XCIN) = 32.768 kHz

•Port processing

Input port: Fixed to “H” or “L” level on the external

Output port: Fixed to output level that does not cause current flow to the external

(Example) When a circuit turns on LED at “L” output level, fix the

output level to “H”.

I/O port: Input port

→ Fixed to “H” or “L” level on the external

Output port

→ Output of data that does not consume current

VREF: Stop to supply to reference voltage input pin by external circuit

Figure 2.11.3 shows the status transition diagram during power failure and Figure 2.11.4 shows the

setting of relevant registers.

Fig. 2.11.3 Status transition diagram during power failure

38B5 Group

Power failure detection signal

Input port

(Note)

Note: Signal is detected by inputting to each input port,

interrupt input pin, and analog input pin.

XIN

XCIN

Internal

system clock

Change internal system

clock to high-speed

mode

After detecting, change internal system clock to

low-speed mode and stop oscillating XIN-XOUT

Middle-speed

mode

High-speed mode

Low-speed mode

XCIN-XCOUT oscillation function selected

Reset released

Power failure detected

M38B53M4-059FP Datasheet(PDF) 240 Page - Mitsubishi Electric Semiconductor

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