MC68HC05E0 Datasheet, PDF (17/96 Pages) Motorola, Inc – High-density complementary metal oxide semiconductor (HCMOS) microcontroller unit

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FUNCTIONAL PIN DESCRIPTION
All signal inputs on the MC68HC05E0 except RESET and OSC1 are TTL compatible.
2.1
VDD and VSS
Power is supplied to the microcontroller via two VDD and two VSS pins. VDD is the positive supply
and VSS is ground.
2.2
OSC1/OSC2
These pins provide control input for an on-chip clock oscillator circuit. A crystal, ceramic resonator
or external clock signal connected to these pins provides the oscillator clock. The oscillator
frequency is divided by 2 to provide the internal bus frequency.
2.2.1 Crystal
The circuit shown in Figure 2-1(b) is recommended when using a crystal. The internal oscillator is
designed to interface with an AT-cut parallel-resonant quartz crystal resonator in the frequency
range specified for fosc (refer to Section 9.5). Use of an external CMOS oscillator is recommended
when crystals outside the specified ranges are to be used. The crystal and components should be
mounted as close as possible to the input pins to minimise output distortion and startup
stabilization time.
2.2.2 Ceramic Resonator
A ceramic resonator may be used in place of the crystal in cost-sensitive applications. The circuit
in Figure 2-1(b) is recommended when using a ceramic resonator. Figure 2-1(a) lists the
MC68HC05E0
FUNCTIONAL PIN DESCRIPTION
MOTOROLA
2-1