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RL78/G1A CHAPTER 5 CLOCK GENERATOR
R01UH0305EJ0200 Rev.2.00 162
Jul 04, 2013
5.4.3 High-speed on-chip oscillator
The high-speed on-chip oscillator is incorporated in the RL78/G1A. The frequency can be selected from among 32, 24,
16, 12, 8, 6, 4, 3, 2, or 1 MHz by using the option byte (000C2H). Oscillation can be controlled by bit 0 (HIOSTOP) of the
clock operation status control register (CSC). The high-speed on-chip oscillator automatically starts oscillating after reset
release.
5.4.4 Low-speed on-chip oscillator
The low-speed on-chip oscillator is incorporated in the RL78/G1A.
The low-speed on-chip oscillator clock is used only as the watchdog timer, real-time clock, and 12-bit interval timer
clock. The low-speed on-chip oscillator clock cannot be used as the CPU clock.
This clock operates when bit 4 (WDTON) of the option byte (000C0H), bit 4 (WUTMMCK0) of the subsystem clock
supply mode control register (OSMC), or both are set to 1.
Unless the watchdog timer is stopped and WUTMMCK0 is a value other than zero, oscillation of the low-speed on-chip
oscillator continues. Note that only when the watchdog timer is operating and the WUTMMCK0 bit is 0, oscillation of the
low-speed on-chip oscillator will stop while the WDSTBYON bit is 0 and operation is in the HALT, STOP, or SNOOZE
mode. While the watchdog timer operates, the low-speed on-chip oscillator clock does not stop even if the program
freezes.
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