NEC 78K0S/K 1+ Series, Примечание к применению

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CHAPTER 4 SETTING METHODS
Application Note U18752EJ2V0AN
17
4.5 Clock Setting
(1) Clock frequency setting
The CPU clock frequency (f
CPU
) and the frequency of the clock supplied to peripheral hardware (f
XP
) are
generated by dividing the frequency of the system clock set with the option byte.
The PPCC and PCC registers are used to select the CPU clock frequency (f
CPU
) and the frequency of the clock
supplied to peripheral hardware (f
XP
).
In this sample program, the PPCC and PCC registers are set as described in
27H
[Example 1] , mentioned later, so
that f
CPU
= f
XP
= 2 MHz.
Figure 4-3. Formats of Processor Clock Control Register (PCC) and Preprocessor Clock Control Register
(PPCC)
Cautions 1. Bits 2 to 7 of PPCC and bits 0 and 2 to 7 of PCC must be set to 0.
2. The clock frequency range that can be used varies, depending on the power supply voltage.
Resonator Conditions CPU Clock Frequency (f
CPU
) Peripheral Hardware Clock
Frequency (f
XP
)
4.0 to 5.5 V 125 kHz
≤
f
CPU
≤
10 MHz
3.0 to 4.0 V 125 kHz
≤
f
CPU
≤
6 MHz
2.7 to 3.0 V 125 kHz
≤
f
CPU
≤
5 MHz
500 kHz
≤
f
XP
≤
10 MHz
Ceramic
resonator, crystal
resonator,
external clock
2.0 to 2.7 V
Note
125 kHz
≤
f
CPU
≤
2 MHz 500 kHz
≤
f
XP
≤
5 MHz
4.0 to 5.5 V 500 kHz (TYP.)
≤
f
CPU
≤
8 MHz (TYP.)
2.7 to 4.0 V 500 kHz (TYP.)
≤
f
CPU
≤
4 MHz (TYP.)
2 MHz (TYP.)
≤
f
XP
≤
8 MHz (TYP.)
High-speed
internal oscillator
2.0 to 2.7 V
Note
500 kHz (TYP.)
≤
f
CPU
≤
2 MHz (TYP.) 2 MHz (TYP.)
≤
f
XP
≤
4 MHz (TYP.)
Note Use standard products and (A)-grade products within a voltage range of 2.2 to 5.5 V, since the detection
voltage (V
POC
) of the power-on-clear (POC) circuit is 2.1 V
±
0.1 V.
Use (A2)-grade products within a voltage range of 2.26 to 5.5 V, since the detection voltage (V
POC
) of the
power-on-clear (POC) circuit is 2.26 V (MAX.).
Remark f
X
: System clock frequency
The system clock to be used is set using the option byte. For details, refer to
28H
4.1 Option Byte Setting .
PPCC
0 0 0 0 0 0 PPCC1 PPCC0
PCC
0 0 0 0 0 0 PCC1 0
PPCC1 PPCC0 PCC1 CPU Clock
Frequency
(f
CPU
)
Peripheral Hardware
Clock Frequency
(f
XP
)
0 0 0 f
X
f
X
0 0 1 f
X
/4 f
X
0 1 0 f
X
/2 f
X
/2
0 1 1 f
X
/8 f
X
/2
1 0 0 f
X
/4 f
X
/4
1 0 1 f
X
/16 f
X
/4
Other than the above Setting prohibited