NEC mPD78F0730, Предварительное руководство пользователя

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CHAPTER 5 CLOCK GENERATOR
Preliminary User’s Manual U19014EJ1V0UD
103
(2) Example of setting procedure when using internal high-speed oscillation clock as CPU clock and
peripheral hardware clock
<1>
•
Restarting oscillation of the internal high-speed oscillation clock
Note
(See 5.6.2 (1) Example of setting procedure when restarting internal high-speed oscillation
clock ).
•
Oscillating the high-speed system clock
Note
(This setting is required when using the high-speed system clock as the peripheral hardware clock.
See 5.6.1 (1) Example of setting procedure when oscillating the X1 clock and (2) Example of
setting procedure when using the external main system clock. )
Note The setting of <1> is not necessary when the internal high-speed oscillation clock or high-
speed system clock is already operating.
<2> Selecting the clock supplied as the main system clock and peripheral hardware clock (MCM register)
Set the main system clock and peripheral hardware clock using XSEL and MCM0.
Selection of Main System Clock and Clock Supplied to Peripheral Hardware XSEL MCM0
Main System Clock (f
XP
) Peripheral Hardware Clock (f
PRS
)
0 0
0 1
Internal high-speed oscillation clock
(f
RH
)
Internal high-speed oscillation clock
(f
RH
)
Caution If the internal high-speed oscillation clock is selected as the main system clock, a clock
other than the internal high-speed ocsillation clock cannot be set as the peripheral
hardware clock.
<3> Selecting the CPU clock division ratio (PCC register)
When CSS is cleared to 0, the main system clock is supplied to the CPU. To select the CPU clock
division ratio, use PCC0, PCC1, and PCC2.
CSS PCC2 PCC1 PCC0 CPU Clock (f
CPU
) Selection
0 0 0 f
XP
0 0 1 f
XP
/2 (default)
0 1 0 f
XP
/2
2
0 1 1 f
XP
/2
3
1 0 0 f
XP
/2
4
0
Other than above Setting prohibited
(3) Example of setting procedure when stopping the internal high-speed oscillation clock
The internal high-speed oscillation clock can be stopped in the following two ways.
•
Executing the STOP instruction to set the STOP mode
•
Setting RSTOP to 1 and stopping the internal high-speed oscillation clock
(a) To execute a STOP instruction
<1> Setting of peripheral hardware
Stop peripheral hardware that cannot be used in the STOP mode (for peripheral hardware that
cannot be used in STOP mode, see CHAPTER 14 STANDBY FUNCTION ).
<2> Setting the X1 clock oscillation stabilization time after standby release
When the CPU is operating on the X1 clock, set the value of the OSTS register before the STOP
instruction is executed.
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