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CHAPTER 5 CLOCK GENERATOR
User’s Manual U19780EJ2V0UD
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(b) To stop X1 oscillation (disabling external clock input) by setting MSTOP 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 high-speed system
clock.
When CLS = 0 and MCS = 1, the high-speed system clock is supplied to the CPU, so change the
CPU clock to a clock other than the high-speed system clock.
•
78K0/KB2-A
MCS
CPU Clock Status
0
Internal high-speed oscillation clock
1
High-speed system clock
•
78K0/KC2-A
CLS
MCS
CPU Clock Status
0
0
Internal high-speed oscillation clock
0
1
High-speed system clock
1
×
Subsystem clock
<2> Stopping the high-speed system clock (MOC register)
When MSTOP is set to 1, X1 oscillation is stopped (the input of the external clock is disabled).
Caution Be sure to confirm that MCS = 0 or CLS = 1 when setting MSTOP to 1. In addition, stop
peripheral hardware that is operating on the high-speed system clock.
5.6.2 Example of controlling internal high-speed oscillation clock
The following describes examples of clock setting procedures for the following cases.
(1) When restarting oscillation of the internal high-speed oscillation clock
(2) When using internal high-speed oscillation clock as CPU clock, and internal high-speed oscillation clock or
high-speed system clock as peripheral hardware clock
(3) When stopping the internal high-speed oscillation clock