68HC05CT4 datasheet(22/142 Pages) FREESCALE

22 / 142 page

General Description

General Release Specification

MC68HC05CT4 — Rev. 2.0

General Description

NOTE:

The voltage on the IRQ pin affects the mode of operation. See Section

6. Operating Modes.

1.4.4 OSC1 and OSC2

These pins provide control input for an on-chip clock oscillator circuit that

drives the PLL reference source. A crystal resonator, a ceramic

resonator, or an external signal connects to these pins providing a

system clock. The oscillator frequency is selectable between 5 or 40

times the internal bus rate. Typical oscillator configurations and

component values are shown in Figure 1-4. The manufacturer of the

crystal should be consulted, since actual component values are

dependent on the type of crystal used.

Figure 1-4. Oscillator Connections

1.4.5 Reset (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.

OSC1

OSC2

OSC1

OSC2

MCU

EXTERNAL CLOCK

UNCONNECTED

(a) Crystal/Ceramic Resonator

(b) External Clock Source

10 M

Ω

10.24 MHz

Oscillator Connections

Connections

15 pF

Freescale Semiconductor, Inc.

For More Information On This Product,

Go to: www.freescale.com

68HC05CT4 Datasheet(PDF) 22 Page - Freescale Semiconductor, Inc