Clock-Generating Circuit - Renesas M16C Series User Manual

M30240 Group
1.2.5.2 Software Reset
Writing a "1" to bit 3 of the processor mode register 0 (address 0004
the microcomputer. A software reset has almost the same effect as a hardware reset with the following
exceptions:
The contents of internal RAM are preserved
USB registers (0300
(000C ), and Frequency synthesizer related registers (03DB
16

1.2.6 Clock-Generating Circuit

The clock-generating circuit contains one oscillator circuit that supplies the operating clock sources to
the CPU and internal peripheral units. Table 1.5 shows the main clock generating circuits.
Table 1.5: Main clock-generating circuits
Functions
Use of clock
Usable oscillator
Pins to connect oscillator
Oscillation stop/restart function
Oscillator status immediately after reset
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. Circuit constants in Figure 1.11 vary
with each oscillator used. Use circuit constant values recommended by the oscillator manufacturer.
Microcomputer
(Built-in feedback resistor)
X
in
C
in
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.
Figure 1.11: Examples of clock source
1.2.6.1 Clock Control
Figure 1.12 shows the block diagram of the clock-generating circuit.
Rev.1.00 Sep 24, 2003 Page 22 of 360
to 033C ), USB attach/detach register (001F
16 16
X
out
(Note)
R
d
C
out
) applies a (software) reset to
16
-03DF ) values are preserved.
16 16
Main clock-generating circuit
• CPU's operating clock source
• Internal peripheral units' operating clock source
Ceramic or crystal oscillator
Xin
, Xout
Available
Oscillating
Microcomputer
(Built-in feedback resistor)
X
in
Externally derived clock
Vcc
Vss
Clock-Generating Circuit
), USB control register
16
X
out
Open