M34282M1 View Datasheet(PDF) - Renesas Electronics

Part Name

Description

Manufacturer

M34282M1

SINGLE-CHIP 4-BIT CMOS MICROCOMPUTER

Renesas Electronics 

4282 Group

• Program counter (PC) .............................................................. 0 0 0 0 0 0 0 0 0 0 0

Address 0 in page 0 is set to program counter.

• Power down flag (P) ................................................................. 0

• Timer 1 underflow flag (T1F) ................................................... 0

• Timer 2 underflow flag (T2F) ................................................... 0

• Timer control register V1 .......................................................... 0 0 0

• Timer control register V2 .......................................................... 0 0 0 0

• Port CARR output flag (CAR) .................................................. 0

• Pull-down control register PU0 ................................................ 0 0 0 0

• Pull-down control register PU1 ................................................ 0 0 0 0

• Logic operation selection register LO ...................................... 0 0

• Most significant ROM code reference enable flag (URS)

0

• Carry flag (CY) ......................................................................... 0

• Register A ................................................................................. 1 1 1 1

• Register B ................................................................................. 1 1 1 1

• Register X ................................................................................. 0 0

• Register Y ................................................................................. 0 0 0 0

• Stack pointer (SP) .................................................................... 1 1

Fig. 20 Internal state at reset

VOLTAGE DROP DETECTION CIRCUIT

The built-in voltage drop detection circuit is designed to detect a

drop in voltage at operating and to reset the microcomputer if

the supply voltage drops below the specified value (Typ. 1.50 V)

or less.

The voltage drop detection circuit is stopped and power

dissipation is reduced in the RAM back-up mode with the

initialized CPU stopped.

VDD

Reset voltage

TYP 1.5V

(Note)

Internal reset signal

Microcomputer starts operation

after f(XIN) is counted to 16384 times.

Note: The voltage drop detection circuit does not have

the hysteresis characteristics in the detected voltage.

Fig. 21 Voltage drop detection circuit operation waveform

Note on voltage drop detection circuit

The voltage drop detection circuit detection voltage of this

product is set up lower than the minimum value of the supply

voltage of the recommended operating conditions.

A battery exchange of an application product is explained as

an example.

The supply voltage falls below to the recommended operating

voltage while CPU keeps active. Then, an unexpected

oscillation-stop, which does not happen by POF instruction

occurs before the supply voltage falls below to the detection

voltage. In this time, even if the supply voltage re-goes up to

the recommended operating voltage, since reset does not

occur, MCU may not operate correctly.

Please confirm the oscillator you use and the frequency of

system clock, and test the operation of your system sufficiently.

VDD

Recommended operatng

condition min.value

VDET

VDD

Recommended

operatng condition

min.value

VDET

Oscillation is stopped

incorrectly.

Even if the voltage re-goes up to

the recommended operating voltage,

MCU may not operate correctly.

→ Normal operation

Rev.1.33 Mar 18, 2004 page 18 of 67

Fig. 22 VDD and VDET

Reset

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