
1-21
Unde
Specifications in this manual are tentative and subject to change
Rev. G
Clock Generating Circuit
MITSUBISHI MICROCOMPUTERS
M30222 Group
SINGLE-CHIP 16-BIT CMOS MICROCOMPUTER
Clock generating Circuit
The clock generating circuit contains two oscillator circuits that supply the operating clock sources to
the CPU and internal peripheral units. Table 1.10 shows some examples of the main clock and
subclock generating circuits.
Table 1.10. Main clock and sub-clock generating circuits
Figure 1.11 shows some examples of the main clock circuit, one using an oscillator connected to the
circuit, and the other one using an externally derived clock for input. Figure 1.12 shows some ex-
amples of sub-clock circuits, one using an oscillator connected to the circuit, and the other one using
an externally derived clock for input. Circuit constants in Figures 1.11 and 1.12 vary with each oscil-
lator used. Use the values recommended by the manufacturer of your oscillator.
Note: Max. voltage is the same as VDC
Main clock generating circuit
Sub-clock generating circuit
Use of clock
Operating clock source for CPU
Operating clock source for Internal
peripheral
Operating clock source
Count clock source for Timers A/B
Operating clock source for LCD
Usable oscillator
Ceramic or crystal oscillator
Crystal oscillator
Pins to connect oscillator
Xin, Xout
Xcin, Xcout
Oscillation stop/restart function
Available
Available
Oscillator status immediately
after Reset
Oscillating
Stopped
Other
Externally derived clock can be input (Note)
Fig. 1.11. Examples of main clock
Microcomputer
X
in
X
out
Open
Externally derived clock
Vcc
Vss
Microcomputer
(Built-in feedback resistor)
X
in
X
out
R
d
C
in
C
out
(Note)
Note: Insert a damping resistor if required. The resistance will vary depending on the oscillator and the oscillation drive
capacity setting. Use the value recommended by the maker of the oscillator.
When the oscillation drive capacity is set to low, check that oscillation is stable. Also, if the oscillator manufacturer's
data sheet specifies that a feedback resistor be added external to the chip, insert a feedback resistor between X
in
and X
out
following the instruction.