MC68HC705CT4 Datasheet, PDF (21/152 Pages) Freescale Semiconductor, Inc – General Release Specification

Freescale Semiconductor, Inc.
General Description
Signal Description
The IRQ pin contains an internal Schmitt trigger as part of its input to
improve noise immunity.
NOTE: The voltage on the IRQ pin affects the mode of operation. See Section
6. Operating Modes.
CAUTION:
Port C interrupt is an external interrupt provided by port C that is
generated when the part comes out of reset. Therefore, an interrupt is
pending that is not being serviced until the CLI instruction is executed.
This interrupt is produced because the state of mask option register
(MOR) is not known until a few clock cycles after the part comes out of
reset. After this interrupt occurs, normal operation resumes, unless the
part is put in reset again.
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.
MCU
OSC1
OSC2
10 MΩ
15 pF
10.24 MHz
15 pF
MCU
OSC1
OSC2
UNCONNECTED
< EXTERNAL CLOCK
(a) Crystal/Ceramic Resonator
Oscillator Connections
(b) External Clock Source
Connections
Figure 1-4. Oscillator Connections
MC68HC705CT4 — Rev. 2.0
MOTOROLA
General Release Specification
General Description
21
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