Renesas rl78 User Manual

 

RL78/G1A 

 

CHAPTER  5   CLOCK  GENERATOR 

R01UH0305EJ0200  Rev.2.00 

 

 

162  

Jul 04, 2013 

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. 

 

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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