68HC705RC17 datasheet(21/126 Pages) FREESCALE

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General Description

Signal Description

MC68HC705RC17 — Rev. 2.0

General Release Specification

General Description

An external clock should be applied to the OSC1 input with the OSC2 pin

not connected (see Figure 1-4 (b)). This setup can be used if the user

does not want to run the CPU with a crystal.

NOTE:

The PLL design requires a 32.768-kHz external frequency for proper

operation.

Figure 1-4. Oscillator Connections

1.5.4 RESET

This active-low pin is used to reset the MCU to a known startup state by

pulling RESET low. The RESET pin contains an internal Schmitt trigger

as part of its input to improve noise immunity. See Section 5. Resets.

1.5.5 LPRST

The LPRST pin is an active-low pin and is used to put the MCU into low-

power reset mode. In low-power reset mode the MCU is held in reset

with all processor clocks halted. See Section 5. Resets.

OSC1

OSC2

OSC1

OSC2

MCU

EXTERNAL CLOCK

UNCONNECTED

(a) Crystal/Ceramic Resonator

(b) External Clock Source

10 M

Ω

Oscillator Connections

Connections

30 pF

Freescale Semiconductor, Inc.

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68HC705RC17 数据表(PDF) 21 Page - Freescale Semiconductor, Inc

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