NEC 78K0S/K 1+ Series, Application Note

Page: 19 / 44

CHAPTER 4 SETTING METHODS
[Example 2] f
CPU
= f
X
/8, f
XP
= f
X
/2
(When “high-speed internal oscillation clock (8 MHz (TYP.))” is selected as the system clock (f
X
) by the
option byte setting, the CPU clock frequency (f
CPU
) is 1 MHz (= 8 MHz/8) and the peripheral hardware
clock frequency (f
XP
) is 4 MHz (= 8 MHz/2).)
PPCC
MOV PPCC, #00000001B
MOV PCC, #00000010B
PPCC = 0b00000001;
PCC = 0b00000010;
Remark f
X
: System clock frequency
The system clock to be used is set using the option byte. For details, refer to 4.1 Option Byte Setting .
The PPCC register setting value is “000000 01 (bits 2 to 7 must be set to 0)” and the PCC register setting value is
“000000 1 0 (bits 0 and 2 to 7 must be set to 0)”.
The clock frequency range that can be used varies, depending on the power supply voltage, so caution is required
when setting the PPCC and PCC. (For details, refer to Figure 4-3. Formats of Processor Clock Control
Register (PCC) and Preprocessor Clock Control Register (PPCC) .)
• Assembly language
• C language
0 0 0 0 0 0 0 1
PCC
0 0 0 0 0 0 1 0
PPCC1 PPCC0 PCC1 CPU Clock
Frequency
(f
CPU
)
Peripheral
Hardware Clock
Frequency (f
XP
)
0 1 1 f
X
/8 f
X
/2
Application Note U18752EJ2V0AN
19