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Recover Chip Freescale MC68705S3

We can Recover Chip Freescale MC68705S3, please view the chip features for your reference:

2.1 VDD, VSS, and EVSS

Power is supplied to the MCU through VDD and VSS. VSS is the power supply, and VSS is ground. EVSS, available on the 44-pin PLCC, is an additional ground pin that must be grounded with VSS. The MCU operates from a single 5-volt (nominal) power supply. Very fast signal transitions occur on the MCU pins. The short rise and fall times place high, short duration current demands on the power supply. To prevent noise problems, provide good power supply bypassing at the MCU. Also, use bypass capacitors that have good high-frequency characteristics and situate them as close to the MCU as possible. Bypass requirements vary, depending on how heavily the MCU pins are loaded.

2.2 Reset (RESET)

An active low bidirectional control signal, RESET, acts as an input to initialize the MCU to a known startup state. It also acts as an open-drain output to indicate that an internal failure has been detected in either the clock monitor or COP watchdog circuit. The CPU distinguishes between internal and external reset conditions by sensing whether the reset pin rises to a logic one in less than two E-clock cycles after a reset has occurred. It is not advisable to connect an external resistor-capacitor (RC) power-up delay circuit to the reset pin of M68HC11 devices because the circuit charge time constant can cause the device to misinterpret the type of reset that occurred. Refer to

SECTION 5 RESETS AND INTERRUPTS for further information.

Figure 2-3 illustrates a reset circuit that uses an external switch. Use a low voltage interrupt circuit, however, to prevent corruption of RAM.

2.3 Crystal Driver and External Clock Input (XTAL, EXTAL)

These two pins provide the interface for either a crystal or a CMOS compatible clock to control the internal clock generator circuitry. The frequency applied to these pins is four times higher than the desired E-clock rate. The XTAL pin is normally left unterminated when an external CMOS compatible clock input is connected to the EXTAL pin. However, a 10 kΩ to 100 kΩ load resistor connected from XTAL to ground can be used to reduce RFI noise emission. The XTAL output is normally intended to drive only a crystal. The XTAL output can be buffered with a high impedance buffer, or it can be used to drive the EXTAL input of another M68HC11.

In all cases, use caution around the oscillator pins. Load capacitances shown in the oscillator circuits include all stray layout capacitances. Refer to Figure 2-4, Figure 2-5, and Figure 2-6.