Freescale Semiconductor, Inc.
General Description
VDD and VSS Pins
1.6 VDD a nd VSS Pins
Power is supplied to the MCU through V and V . V is the positive
DD
SS DD
supply, and V is ground. The MCU operates from a single power
SS
supply.
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, special care should be taken to
provide good power supply bypassing at the MCU by using bypass
capacitors with good high-frequency characteristics that are positioned
as close to the MCU as possible. Bypassing requirements vary,
depending on how heavily the MCU pins are loaded.
1.7 OSC1 a nd OSC2 Pins
The OSC1 and OSC2 pins are the connections for the external pin
oscillator (EPO). The OSC1 and OSC2 pins can accept the following
sets of components:
1. A crystal as shown in Figure 1-3 (a)
2. A ceramic resonator as shown in Figure 1-3 (a)
3. An external resistor as shown in Figure 1-3 (b)
4. An external clock signal as shown in Figure 1-3 (c)
The selection of the crystal/ceramic resonator or RC oscillator
configuration is done by product part number selection as described in
Section 17. Ordering Information.
The frequency, f , of the EPO or external clock source is divided by two
osc
to produce the internal operating frequency, f . An internal 2 MΩ
OP
resistor may be selected between OSC1 and OSC2 by the OSCRES bit
in the mask option register (MOR).
MC68HC705JJ7/MC68HC705JP7 — Rev. 3.0
General Release Specification
General Description
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