M16C65 Datasheet, PDF (152/829 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
8.3.5 125 kHz On-Chip Oscillator Clock (fOCO-S)
This clock is approximately 125 kHz, and is supplied by the 125 kHz on-chip oscillator. It is used as the
clock source for the CPU and peripheral function clocks. In addition, when the CSPRO bit in the CSPR
register is 1 (count source protection mode enabled), this clock is used as the count source for the
watchdog timer (refer to 15.4.2 “Count Source Protection Mode Enabled”).
After reset, the fOCO-S divided by 8 is used as the CPU clock.
If the main clock stops oscillating and the FRA01 bit is 0, when the CM20 bit in the CM2 register is 1
(oscillation stop/re-oscillation detection function enabled) and the CM27 bit is 1 (oscillation stop/re-
oscillation detection interrupt), the 125 kHz on-chip oscillator automatically starts operating and
supplying the necessary clock for the MCU.
Follow the steps below to start or stop the fOCO-S. Refer to 8.2 “Registers” for access to register and
bit.
fOCO-S start
(1) Set the CM14 bit in the CM1 register to 0 (125 kHz on-chip oscillator on).
(2) Wait for td (OCOS).
fOCO-S stop
(1) Set the CM14 bit in the CM1 register to 1 (125 kHz on-chip oscillator off).
When the CM21 bit is 1 (on-chip oscillator used as the clock source for the CPU), the CM14 bit
becomes 0 (125 kHz on-chip oscillator on).
REJ09B0484-0030 Rev.0.30 Sep 09, 2008
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