Mitsubishi microcomputers
M16C / 62P Group
SINGLE-CHIP 16-BIT CMOS MICROCOMPUTER
Clock Generation Circuit
58
development
Preliminary Specifications Rev.1.0
Specifications in this manual are tentative and subject to change.
Microcomputer
(Built-in feedback resistor)
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.
Figure 1.9.7. Examples of Main Clock Connection Circuit
The following describes the clocks generated by the clock generation circuit.
(1) Main Clock
This clock is used as the clock source for the CPU and peripheral function clocks. This clock is used as
the clock source for the CPU and peripheral function clocks. The main clock oscillator circuit is configured
by connecting a resonator between the X
IN
and X
OUT
pins. The main clock oscillator circuit contains a
feedback resistor, which is disconnected from the oscillator circuit during stop mode in order to reduce the
amount of power consumed in the chip. The main clock oscillator circuit may also be configured by
feeding an externally generated clock to the X
IN
pin. Figure 1.9.7 shows the examples of main clock
connection circuit.
After reset, the main clock divided by 8 is selected for the CPU clock.
The power consumption in the chip can be reduced by setting the CM05 bit of CM0 register to “1” (main
clock oscillator circuit turned off) after switching the clock source for the CPU clock to a sub clock or ring
oscillator clock. In this case, X
OUT
goes “H”. Furthermore, because the internal feedback resistor remains
on, X
IN
is pulled “H” to X
OUT
via the feedback resistor. Note that if an externally generated clock is fed into
the X
IN
pin, the main clock cannot be turned off by setting the CM05 bit to “1”. If necessary, use an
external circuit to turn off the clock.
During stop mode, all clocks including the main clock are turned off. Refer to “power control”.