CHAPTER 5 CLOCK GENERATOR
Preliminary User’s Manual U19014EJ1V0UD
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(4) Main OSC control register (MOC)
This register selects the operation mode of the high-speed system clock.
This register is used to stop the X1 oscillator or to disable an external clock input from the EXCLK pin when the
CPU operates with a clock other than the high-speed system clock.
MOC can be set by a 1-bit or 8-bit memory manipulation instruction.
Reset signal generation sets this register to 80H.
Figure 5-5. Format of Main OSC Control Register (MOC)
Address: FFA2H After reset: 80H R/W
Symbol
<7>
6 5 4 3 2 1 0
MOC
MSTOP
0 0 0 0 0 0 0
Control of high-speed system clock operation
MSTOP
X1 oscillation mode
External clock input mode
0
X1 oscillator operating
External clock from EXCLK pin is enabled
1
X1 oscillator stopped
External clock from EXCLK pin is disabled
Cautions 1. When setting MSTOP to 1, be sure to confirm that the CPU operates with a clock
other than the high-speed system clock. Specifically, set MSTOP to 1 under the
following condition.
•
When MCS = 0 (when CPU operates with the internal high-speed oscillation
clock)
2. Do not clear MSTOP to 0 while bit 6 (OSCSEL) of the clock operation mode select
register (OSCCTL) is 0 (I/O port mode).
3. The peripheral hardware cannot operate when the peripheral hardware clock is
stopped. To resume the operation of the peripheral hardware after the
peripheral hardware clock has been stopped, initialize the peripheral hardware.
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