M16C65 Datasheet, PDF (149/829 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.
8. Clock Generator
The XOUT becomes high by setting the CM05 bit in the CM0 register to 1 (main clock oscillator circuit
turned off) after switching the clock source for the CPU clock to the sub clock (fC) or on-chip oscillator
clock (fOCO-F, fOCO-S). In this case, the XIN is pulled high to the XOUT via the feedback resistor
because the internal feedback resistor remains connected.
When the main clock oscillator circuit is not used, setting the CM13 bit in the CM1 register to 1 enables to
select the internal feedback resistor not connected.
Perform the following steps to start or stop the main clock. Refer to 8.2 “Registers” for access to register
and bit.
Main clock oscillation start
(1) Set the CM15 bit to 1 (drive capacity high) when a resonator is connected between pins XIN and
XOUT.
(2) Set the CM05 bit to 0 (main clock oscillating).
(3) Wait until main clock oscillation stabilizes. (Enter the external clock when entering it from the XIN
pin.)
Main clock oscillation stop
(1) Set the CM20 bit in the CM2 register to 0 (oscillation stop/re-oscillation detection function
disabled).
(2) Set the CM05 bit to 1 (stop).
(3) Stop the external clock (when entering the external clock from the XIN pin).
REJ09B0484-0030 Rev.0.30 Sep 09, 2008
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