MC68HC11A0P1 View Datasheet(PDF) - Freescale Semiconductor

Part Name

Description

Manufacturer

MC68HC11A0P1

ROM-based high-performance microcontrollers

Freescale Semiconductor 

Freescale Semiconductor, Inc.

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.

VDD

VDD

2

IN

1

RESET

MC34(0/1)64

GND

3

4.7 k Ω

TO RESET

OF M68HC11

EXT RESET CIRCUIT

Figure 2-3 External Reset Circuit

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 con-

nected 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.

EXTAL

MCU

XTAL

10 MΩ

25 pF *

4xE

CRYSTAL

25 pF *

* THIS VALUE INCLUDES ALL STRAY CAPACITANCES.

Figure 2-4 Common Crystal Connections

TECHNICAL DATA

PIN DESCRIPTIONS

For More Information On This Product,

Go to: www.freescale.com

COMMON XTAL CONN

2-3

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