Freescale Semiconductor, Inc.
General Release Specification
Functional Pin Description
1.4 Func tiona l Pin De sc rip tion
The following paragraphs describe the functionality of each pin on the
MC68HC705P6A package. Pins connected to subsystems described in
other chapters provide a reference to the chapter instead of a detailed
functional description.
1.4.1 V a nd V
DD
SS
Power is supplied to the MCU through V and V . V is connected
DD
SS
DD
to a regulated +5 volt supply and V is connected to ground.
SS
Very fast signal transitions occur on the MCU pins. The short rise and
fall times place very high short-duration current demands on the power
supply. To prevent noise problems, take special care to provide good
power supply bypassing at the MCU. Use bypass capacitors with good
high-frequency characteristics and position them as close to the MCU as
possible. Bypassing requirements vary, depending on how heavily the
MCU pins are loaded.
1.4.2 OSC1 a nd OSC2
The OSC1 and OSC2 pins are the control connections for the on-chip
oscillator. The OSC1 and OSC2 pins can accept the following:
1. A crystal as shown in Figure 1-2(a)
2. A ceramic resonator as shown in Figure 1-2(a)
3. An external clock signal as shown in Figure 1-2(b)
The frequency, f , of the oscillator or external clock source is divided
osc
by two to produce the internal bus clock operating frequency, f . The
op
oscillator cannot be turned off by software unless the MOR bit, SWAIT,
is clear when a STOP instruction is executed.
MC68HC705P6A — Rev. 1.0
General Release Specification
General Description
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