EM78P258N
8-Bit Microprocessor with OTP ROM
The RC Oscillator frequencies:
Cext
Rext
3.3k
Average Fosc 5V,25°C
Average Fosc 3V,25°C
3.5 MHz
2.5 MHz
1.30 MHz
140 KHz
1.27 MHz
850 KHz
450 KHz
48 KHz
3.2 MHz
2.3 MHz
1.25 MHz
140 KHz
1.21 MHz
820 KHz
450 KHz
50 KHz
5.1k
10k
20 pF
100k
3.3k
5.1k
10k
100 pF
300 pF
100k
3.3k
5.1k
10k
560 KHz
370 KHz
196 KHz
20 KHz
540 KHz
360 KHz
192 KHz
20 KHz
100k
NOTE: 1. Measured on DIP packages
2. Design reference only
3. The frequency drift is about ±30%
6.10.4 Internal RC Oscillator Mode
EM78P258N offers a versatile internal RC mode with default frequency value of 4MHz.
Internal RC oscillator mode has other frequencies (1MHz, 8MHz, and 455KHz) that can
be set by CODE OPTION (WORD1), RCM1, and RCM0. Table below describes the
EM78P258N internal RC drift with the variation of voltage, temperature, and process.
Internal RC Drift Rate (Ta=25℃, VDD=5V±5%, VSS=0V)
Drift Rate
Internal
RC Frequency
Temperature
(-40℃~+80℃)
Voltage
Process
Total
(2.3V~5.5V)
4MHz
8MHz
±10%
±10%
±10%
±10%
±5%
±6%
±5%
±5%
±4%
±4%
±4%
±4%
±19%
±20%
±19%
±19%
1MHz
455MHz
Theoretical values, for reference only. Actual values may vary depending on actual process.
6.11 Power-on Considerations
Any microcontroller is not warranted to start operating properly before the power supply
stabilizes in steady state. The EM78P258N POR voltage range is 1.9 ~ 2.1V. Under
customer application, when power is switched OFF, Vdd must drop below 1.9V and
remains at OFF state for 10µs before power can be switched ON again. Subsequently,
the EM78P258N will reset and work normally. The extra external reset circuit will work
well if Vdd rises fast enough (50ms or less). However, under critical applications, extra
devices are still required to assist in solving power-on problems.
Product Specification (V1.0) 06.16.2005
• 59
(This specification is subject to change without further notice)
ELAN [ ELAN MICROELECTRONICS CORP ]
