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RL78/G1A CHAPTER 5 CLOCK GENERATOR
R01UH0305EJ0200 Rev.2.00 147
Jul 04, 2013
5.3.3 Clock operation status control register (CSC)
This register is used to control the operations of the high-speed system clock, high-speed on-chip oscillator clock, and
subsystem clock (except the low-speed on-chip oscillator clock).
The CSC register can be set by a 1-bit or 8-bit memory manipulation instruction.
Reset signal generation sets this register to C0H.
Figure 5-4. Format of Clock Operation Status Control Register (CSC)
Address: FFFA1H After reset: C0H R/W
Symbol <7> <6> 5 4 3 2 1 <0>
CSC MSTOP XTSTOP 0 0 0 0 0 HIOSTOP
High-speed system clock operation control
MSTOP
X1 oscillation mode External clock input mode Input port mode
0 X1 oscillator operating External clock from EXCLK
pin is valid
1 X1 oscillator stopped External clock from EXCLK
pin is invalid
Input port
Subsystem clock operation control
XTSTOP
XT1 oscillation mode External clock input mode Input port mode
0 XT1 oscillator operating External clock from EXCLKS
pin is valid
1 XT1 oscillator stopped External clock from EXCLKS
pin is invalid
Input port
HIOSTOP High-speed on-chip oscillator clock operation control
0 High-speed on-chip oscillator operating
1 High-speed on-chip oscillator stopped
Cautions 1. After reset release, set the clock operation mode control register (CMC) before
setting the CSC register.
2. Set the oscillation stabilization time select register (OSTS) before setting the MSTOP
bit to 0 after releasing reset. Note that if the OSTS register is being used with its
default settings, the OSTS register is not required to be set here.
3. To start X1 oscillation as set by the MSTOP bit, check the oscillation stabilization
time of the X1 clock by using the oscillation stabilization time counter status register
(OSTC).
4. When starting XT1 oscillation by setting the XTSTOP bit, wait for oscillation of the
subsystem clock to stabilize by setting a wait time using software.
5. Do not stop the clock selected for the CPU peripheral hardware clock (f
CLK) with the
OSC register.
6. The setting of the flags of the register to stop clock oscillation (invalidate the
external clock input) and the condition before clock oscillation is to be stopped are
as Table 5-2.