mc68hc705k1 Freescale Semiconductor, Inc, mc68hc705k1 Datasheet - Page 23

• Manufacturer Part Number: mc68hc705k1
• Description: Hcmos Microcontroller Unit
• Manufacturer: Freescale Semiconductor, Inc

1.6.2.4 3-Pin RC Oscillator
1.6.2.5 External Clock
MC68HC705K1 — Rev. 2.0
NOTE:
disconnects the internal startup resistor. The PIN3 bit in the mask option
register must remain erased (logic 0). The PIN3 bit selects the 3-pin RC
oscillator configuration. See
Another low-cost option is the 3-pin RC oscillator configuration shown in
Figure
The OSC2 and PB1/OSC3 signals are square waves, and the signal on
OSC1 is a triangular wave. The 3-pin RC oscillator configuration is
recommended for frequencies of 1 MHz and less.
To use the 3-pin RC oscillator configuration, both the RC and PIN3 bits
in the mask option register must be programmed to logic 1s. See
9.6 Mask Option
In 3-pin RC oscillator configurations, the personality EPROM
(PEPROM) cannot be programmed by user software. If the voltage on
IRQ/V
configuration and device operation will be disrupted.
An external clock from another CMOS-compatible device can drive the
OSC1 input, with the OSC2 pin unconnected, as
Freescale Semiconductor, Inc.
For More Information On This Product,
PP
1-8. The 3-pin oscillator is more stable than the 2-pin oscillator.
is raised above V
Figure 1-8. 3-Pin RC Oscillator Connections
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MCU
General Description
R
Register.
+
C3
DD
PB1/OSC3
9.6 Mask Option
, the oscillator will revert to a 2-pin oscillator
C3
Register.
OSC1
OSC2
Figure 1-9
V
V
DD
SS
General Description
C1 C2
R
Pin Assignments
Technical Data
shows.
V
SS