EM78P809NP datasheet(63/75 Pages) EMC

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EM78P809N

8-Bit Microcontroller

Product Specification (V1.0) 07.26.2005

• 59

(This specification is subject to change without further notice)

Bit 6 (CYES) :

Cycle selection for JMP, CALL instruction

CYES = “0” :

One cycle

CYES = “1” :

Two cycles

Bit 4 (OSC) :

Oscillator type selection.

OSC = “0” :

RC type

OSC = “1” :

Crystal type

Bit 3 (HLP) :

Power selection.

HLP = “0” :

Low power

HLP = “1” :

High power

Bit 2~0 (PR2~PR0) :

Protect Bit

PR2~PR0 are write-protect bits, configured as follows:

PR2

PR1

PR0

Protect

Others

Enable

Disable

4.17.2 Customer ID Register

Word 1

Bit 12~Bit 0

XXXXXXXXXXXXX

Word 2

Bit 12~Bit 0

XXXXXXXXXXXXX

Bits 12 ~ 0: Customer’s ID code

4.18 Power-on Considerations

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

supply maintains at its steady state. The EM78P809N has a built-in Power On Voltage

Detector (POVD) with a detecting level of 2.1V. It will work well if VDD rises fast enough

(10 ms or less). In many critical applications, however, additional components are

required to provide solutions on probable power-up problems.

4.18.1 External Power-on Reset Circuit

The circuit shown in Fig. 34 use an external RC to produce the reset pulse. The pulse

width (time constant) should be kept long enough for VDD to reach minimum operation

voltage. This circuit is used when the power supply has slow rise time. Because the

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