EM78F651NAMSSLASHNAMJ datasheet(47/58 Pages) EMC

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EM78F651N

8-Bit Microcontroller

Product Specification (V1.1) 10.20.2006

• 43

(This specification is subject to change without further notice)

Bit 3 and Bit 2 (RCM1, RCM0): RC mode selection bits

RCM 1

RCM 0

*Frequency(MHz)

3.58

455kHz

Bits 1~0 (LVR1 ~ LVR0): Low Voltage Reset Enable bits

LVR1

LVR0

Reset Level

Release Level

2.6V

2.8V

3.3V

3.45V

3.8V

3.9V

LVR1, LVR0=“0, 0”

： LVR disable, power- on reset point of EM78F651N is 2.0V.

LVR1, LVR0=“0, 1”

： If Vdd < 2.6V, the EM78F651N will be reset.

LVR1, LVR0=“1, 0”

： If Vdd < 3.3V, the EM78F651N will be reset.

LVR1, LVR0=“1, 1”

： If Vdd < 3.8V, the EM78F651N will be reset.

6.10.2 Customer ID Register (Word 2)

Bit 12~Bit 0

XXXXXXXXXXXXX

Bits 12~0: Customer’s ID code

6.11 Power-on Considerations

Any microcontroller is not guaranteed to start to operate properly before the power

supply stays has stabilized. The EM78F651N has an on-chip Power-on Voltage

Detector (POVD) with a detecting level of 2.0V. It will work well if Vdd can rise quick

enough (50 ms or less). In many critical applications, however, extra devices are still

required to assist in solving power-up problems.

6.12 External Power-on Reset Circuit

The circuit shown in Fig 6-15 implements an external RC to produce a reset pulse.

The pulse width (time constant) should be kept long enough for Vdd to reached

minimum operation voltage. This circuit is used when the power supply has slow rise

time. Because the current leakage from the /RESET pin is

±5µA, it is recommended

that R should not be greater than 40 K. In this way, the /RESET pin voltage is held

below 0.2V. The diode (D) acts as a short circuit at the moment of power down.

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