EM78P809N
8-Bit Microcontroller
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
Others
1
PR0
Protect
Enable
Disable
1
1
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
Product Specification (V1.0) 07.26.2005
• 59
(This specification is subject to change without further notice)
ELAN [ ELAN MICROELECTRONICS CORP ]
