8-Bit Microcontroller with OTP ROM Specification Sheet

EM78P447N
8-Bit Microcontroller with OTP ROM
28 •
Product Specification (V1.1) 03.30.2005
(This specification is subject to change without further notice)
4.8.2 Customer ID Register (Word 1)
Word 1
Bit 12~Bit 0
XXXXXXXXXXXXX
Bit 12~0: Customer’s ID code
4.9 Power On Considerations
Any microcontroller is not guaranteed to start and operate properly before the power
supply stays at its steady state. EM78P447N is equipped with Power On Voltage
Detector(POVD) with a detecting level is 2.0V. It will work well if Vdd rises fast enough
(10 ms or less). In many critical applications, however, extra devices are still required
to assist in solving power-up problems.
4.10 External Power On Reset Circuit
The circuit shown in Fig.16 implements an external RC to produce the 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 about ±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. The
capacitor C will discharge rapidly and fully. Rin, the current-limited resistor, will prevent
high current or ESD (electrostatic discharge) from flowing to pin /RESET.
EM78P447N
/RESET
Vdd
D
R
Rin
C
Fig. 13 External Power-Up Reset Circuit