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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 follow s:
PR2 PR1 PR0 Protect
Others Enable
1 1 1 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 V
DD 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 V
DD to reach minimum operation
voltage. This circuit is used when the power supply has slow rise time. Because the