Extract Heximal of Secured Microcontroller PIC18F2539 and reprograme the firmware to blank MCU PIC18F2539, security fuse bits will be disable by ultraviole laser cutting and disable the locked mechenism for microcontroller unlocking;

For timing insensitive applications, the “RC” and “RCIO” device options offer additional cost savings. The actual oscillator frequency is a function of several factors:

• supply voltage
• values of the external resistor (REXT) and capacitor (CEXT)
• operating temperature

Given the same device, operating voltage and temperature and component values, there will also be unit-to-unit frequency variations. These are due to factors such as mcu at89c51rd2 eeprom extraction:

• normal manufacturing variation
• difference in lead frame capacitance between package types (especially for low CEXT values)
• variations within the tolerance of limits of REXT and CEXT

In the RC Oscillator mode, the oscillator frequency divided by 4 is available on the OSC2 pin. This signal may be used for test purposes or to synchronize other logic. Figure 2-5 shows how the R/C combination is connected.

The RCIO Oscillator mode (Figure 2-6) functions like the RC mode, except that the OSC2 pin becomes an additional general purpose I/O pin. The I/O pin becomes bit 6 of PORTA (RA6) before the chip code of at89c51ed2 Extraction can be finished.

A Phase Locked Loop (PLL) circuit is provided as an option for users who wish to use a lower frequency oscillator circuit or to clock the device up to its highest rated frequency from a crystal oscillator. This may be useful for customers who are concerned with EMI due to high-frequency crystals or users who require higher clock speeds from an internal oscillator.

The HSPLL mode makes use of the HS mode oscillator for frequencies up to 10 MHz. A PLL then multiplies the oscillator output frequency by 4 to produce an internal clock frequency up to 40 MHz. The PLLEN bit is not available in this oscillator mode. The PLL is only available to the crystal oscillator when the FOSC3:FOSC0 configuration bits are programmed for HSPLL mode (= 0110).