M16C1N Datasheet, PDF (41/238 Pages) Renesas Technology Corp – RENESAS 16-BIT SINGLE-CHIP MICROCOMPUTER M16C FAMILY / M16C/10 SERIES

M16C/1N Group
6. Clock Generation Circuit
6.2 Sub-clock
The sub-clock is generated by the sub-clock oscillation circuit. No sub-clock is generated after a reset.
After oscillation is started using the port Xc select bit (bit 4 at address 000616), the sub-clock can be
selected as BCLK by using the system clock select bit (bit 7 at address 000616). However, be sure that
the sub-clock oscillation has fully stabilized before switching.
After the oscillation of the sub-clock oscillation circuit has stabilized, the drive capacity of the XCOUT pin
can be reduced using the XCIN-XCOUT drive capacity select bit (bit 3 at address 000616). Reducing the
drive capacity of the XCOUT pin reduces the power dissipation. This bit changes to "1" when shifting to
stop mode and at a reset.
Figure 6.7 shows the examples of sub-clock connection circuit.
Microcomputer
(Built-in feedback resistor)
XCIN
XCOUT
(Note 1)
RCd
Microcomputer
(Built-in feedback resistor)
XCIN
XCOUT
Open
Externally derived clock
CCIN
CCOUT
Vcc
Vss
Note 1: 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 6.7 Examples of sub-clock connection circuit
6.3 On-chip Oscillator Clock
This clock by supplied by a on-chip oscillator. The oscillation of the on-ship oscillator can be used as
BCLK by setting the main clock selected bit (bit 2 at address 000C16. Lower power consumption can be
realized because the oscillating frequency of the on-chip oscillator is much lower compared to that of XIN.
The frequency of the on-chip oscillator depends on the supply voltage and the operation temperature
range. The application products must be designed with sufficient margin to accommodate the frequency
range.
Rev.1.00 Oct 20, 2004 page 29 of 222
REJ09B0007-0100Z