MC68HC05X4 Datasheet, PDF (24/156 Pages) Motorola, Inc – HCMOS Microcontroller Unit

Freescale Semiconductor, Inc.
Modes of Operation and Pin Descriptions
MDS/TCAP(VPP)
During reset this pin is used as a mode select input (MDS) to determine
the operating mode. It also serves as the input capture (TCAP) pin for
the 16-bit programmable timer. In addition it is the EPROM programming
voltage input pin (VPP) for the MC68HC705X4 device.
OSC1/OSC2
System clocks
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 (f_OSC) is
divided by 2 or by 10, chosen via a mask option, to provide the internal
bus frequency (f_OP).
The MCU and MCAN system clocks are obtained as shown in the
Figure 7.
f_osc
OSC1
Crystal
Divide by
2
f_osc/2
Divide by
f_OP
10 or 2
Prescaler (P)
2P
t_SCL =
f_osc
MCAN module system clock
MCU bus clock
Figure 7. Oscillator block diagram
The circuit shown in Figure 8(a) 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 DC electrical characteristics). 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 start-up stabilization time.
MC68HC05X4 Rev 1.0
Modes of Operation and Pin Descriptions
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12-modes