MC68HC05P9A Datasheet, PDF (17/158 Pages) Freescale Semiconductor, Inc – HCMOS Microcontroller Unit

Freescale Semiconductor, Inc.
Pin Descriptions
Pin Functions
NOTE:
Because the frequency stability of ceramic resonators is not as high as
that of crystal oscillators, using a ceramic resonator may degrade the
performance of the ADC.
RC Oscillator
The lowest cost oscillator is the
RC oscillator configuration
where a resistor is connected
between the two oscillator pins
as shown in Figure 6. The
internal startup resistor of
approximately 2 MΩ is not
recommended between OSC1
and OSC2 for the RC-type
oscillator.
MCU
OSC1
R
OSC2
Figure 6. RC Oscillator
Connections
External Clock
Connections
RESET
An external clock from another
CMOS-compatible device can
drive the OSC1 input, with the
OSC2 pin unconnected, as
Figure 7 shows.
A logic 0 on the RESET pin
forces the MCU to a known
startup state. The RESET pin
input circuit contains an internal
Schmitt trigger to improve noise
immunity.
MCU
EXTERNAL
CMOS CLOCK
UNCONNECTED
Figure 7. External Clock
Connections
IRQ
The IRQ pin has the following functions:
• Applying asynchronous external interrupt signals
• Applying V_TST, the mode detection voltage
9-mc68hc05p9a
MOTOROLA
Pin Descriptions
17
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