M16C65 Datasheet, PDF (782/829 Pages) Renesas Technology Corp – RENESAS MCU M16C FAMILY / M16C/60

Under development
M16C/65 Group
Preliminary Specification
This is a preliminary specification and is subject to change.
31. Precautions
31.6 Notes on Clock Generator
31.6.1 Oscillation Circuit Using an Oscillator
To connect an oscillator, follow these instructions:
• The oscillation characteristics are tied closely to the user’s board design. Perform a careful evalua-
tion of the board before connecting an oscillator.
• Oscillation circuit structure depends on the oscillator. The M16C/65 Group contains a feedback
resistor, but an external feedback resistor may be required. Contact the oscillator manufacturer
regarding circuit constants, as they are dependent on the oscillator or stray capacitance of the
mounted circuit.
• Check output from the CLKOUT pin to confirm that the clock generated by the oscillation circuit is
properly transmitted to the MCU. Procedures for outputting a clock from the CLKOUT pin are listed
below. Set the clock output from the CLKOUT pin to 25 MHz or below.
Outputting the main clock
(1) Set the PRC0 bit in the PRCR register to 1 (write enabled).
(2) Set the CM11 bit in the CM1 register to 0, the CM07 bit in the CM0 register to 0, and the CM21
bit in the CM2 register to 0 (main clock selected).
(3) Select the clock output from the CLKOUT pin (refer to the following table).
(4) Set the PRC0 bit in the PRCR register to 0 (write disabled)
Table 31.2 Output from CLKOUT Pin When Selecting Main Clock
Bit Setting
PCLKR Register
CM0 Register
PCLK5 Bit
Bits CM01 to CM00
1
00b
0
10b
0
11b
Output from CLKOUT Pin
Clock with the same frequency as the main clock
Main clock divided by 8
Main clock divided by 32
Outputting the sub clock
(1) Set the PRC0 bit in the PRCR register to 1 (write enabled).
(2) Set the CM07 bit in the CM0 register to 1 (sub clock selected).
(3) Set the PCLK5 bit in the PCLKR register to 0, and bits CM01 to CM00 in the CM0 register to 01b
(fC output from CLKOUT pin).
(4) Set the PRC0 bit in the PRCR register to 0 (write disabled)
MCU
XIN
XOUT
VSS
CIN
Rf
feedback
resistor
Oscillator
Rd
damping resistor ^COUT
Figure 31.3 Oscillation Circuit Example
REJ09B0484-0030 Rev.0.30 Sep 09, 2008
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