Renesas M16C Series User Manual

Clock-Generating Circuit
M30240 Group
Rev.1.00 Sep 24, 2003 Page 22 of 360
1.2.5.2 Software Reset
Writing a “1” to bit 3 of the processor mode register 0 (address 0004
16
) applies a (software) reset to
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
16
to 033C
16
), USB attach/detach register (001F
16
), USB control register
(000C
16
), and Frequency synthesizer related registers (03DB
16
-03DF
16
) values are preserved.
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
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.
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.
Functions Main clock-generating circuit
Use of clock
• CPU’s operating clock source
• Internal peripheral units’ operating clock source
Usable oscillator Ceramic or crystal oscillator
Pins to connect oscillator
Xin, Xout
Oscillation stop/restart function Available
Oscillator status immediately after reset Oscillating
Microcomputer
Xin Xout
Externally derived clock
Open
Vcc
Vss
Microcomputer
(Built-in feedback resistor)
Xin
Xout
Rd
Cin
Cout
(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.
(Built-in feedback resistor)

Renesas M16C Series Specifications

General

Brand	Renesas
Model	M16C Series
Category	Computer Hardware
Language	English