CHAPTER 5 CLOCK GENERATOR
Preliminary User’s Manual U19014EJ1V0UD
104
<3> Executing the STOP instruction
When the STOP instruction is executed, the system is placed in the STOP mode and internal high-
speed oscillation clock is stopped.
(b) To stop internal high-speed oscillation clock by setting RSTOP to 1
<1> Confirming the CPU clock status (PCC and MCM registers)
Confirm with CLS and MCS that the CPU is operating on a clock other than the internal high-speed
oscillation clock.
When CLS = 0 and MCS = 0, the internal high-speed oscillation clock is supplied to the CPU, so
change the CPU clock to the high-speed system clock.
CLS
MCS
CPU Clock Status
0
0
Internal high-speed oscillation clock
0
1
High-speed system clock
<2> Stopping the internal high-speed oscillation clock (RCM register)
When RSTOP is set to 1, internal high-speed oscillation clock is stopped.
Caution Be sure to confirm that MCS = 1 or CLS = 1 when setting RSTOP to 1. In addition, stop
peripheral hardware that is operating on the internal high-speed oscillation clock.
5.6.3 Example of controlling internal low-speed oscillation clock
The internal low-speed oscillation clock cannot be used as the CPU clock.
Only the following peripheral hardware can operate with this clock.
•
Watchdog timer
•
8-bit timer H1 (if f
RL
, f
RL
/2
7
, or f
RL
/2
9
is selected as the count clock)
In addition, the following operation modes can be selected by the option byte.
•
Internal low-speed oscillator cannot be stopped
•
Internal low-speed oscillator can be stopped by software
The internal low-speed oscillator automatically starts oscillation after a reset release, and the watchdog timer is
driven (240 kHz (TYP.)) if the watchdog timer operation has been enabled by the option byte.
(1) Example of setting procedure when stopping the internal low-speed oscillation clock
<1> Setting LSRSTOP to 1 (RCM register)
When LSRSTOP is set to 1, the internal low-speed oscillation clock is stopped.
(2) Example of setting procedure when restarting oscillation of the internal low-speed oscillation clock
<1> Clearing LSRSTOP to 0 (RCM register)
When LSRSTOP is cleared to 0, the internal low-speed oscillation clock is restarted.
Caution If “Internal low-speed oscillator cannot be stopped” is selected by the option byte, oscillation of
the internal low-speed oscillation clock cannot be controlled.
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