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RL78/G1P
CHAPTER 5 CLOCK GENERATOR
R01UH0895EJ0100 Rev.1.00
102
Nov 29, 2019
5.3.3 Clock operation status control register (CSC)
This register is used to control the operations of the high-speed system clock and high-speed on-chip oscillator 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
0 0 0 0 0 0
HIOSTOP
MSTOP
High-speed system clock operation control
X1 oscillation mode
External clock input mode
Input port mode
0
X1 oscillator operating
External clock from EXCLK
pin is valid
Input port
1
X1 oscillator stopped
External clock from EXCLK
pin is invalid
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. Do not stop the clock selected for the CPU peripheral hardware clock (f
CLK
) with the
OSC register.
5. The preconditions for stopping oscillation of the various clocks (and for disabling
the external clock inputs) and the flag settings to be made to stop oscillation of each
clock or disable input of the given clock are listed in Table 5-2.
Before stopping the oscillation of a clock, check that the precondition for stopping
clock oscillation is satisfied.
Table 5-2. Preconditions for Stopping Clock Oscillation and Flag Settings
Clock Precondition
for
Stopping Clock Oscillation
(or Disabling External Clock Input)
Flag Settings of
CSC Register
X1 clock
CPU and peripheral hardware clocks operate with a clock
other than the high-speed system clock.
(MCS = 0)
MSTOP = 1
External main system
clock
High-speed on-chip
oscillator clock
CPU and peripheral hardware clocks operate with a clock
other than the high-speed on-chip oscillator clock.
(MCS = 1)
HIOSTOP = 1