Chapter 17 Option Byte - NEC 78K0S/KA1+ Preliminary User's Manual

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The 78K0S/KA1+ has an area called an option byte at address 0080H of the flash memory. When using the
product, be sure to set the following functions by using the option byte.
1. Selection of system clock source
2. Low-speed Ring-OSC clock oscillation
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3. Control of RESET pin
4. Oscillation stabilization time on power application or reset input
07FFH/0FFFH
0080H
0000H
• High-speed Ring-OSC clock
• Crystal/ceramic oscillation clock
• External clock input
• Cannot be stopped.
• Can be stopped by software.
• Used as RESET pin
• RESET pin is used as an input port pin (P34).
• 2
10
/f
X
• 2
12
/f
X
• 2
15
/f
X
• 2
17
/f
X
Figure 17-1. Positioning of Option Byte
Flash memory
×
(2048/4096 8 bits)

CHAPTER 17 OPTION BYTE

Option byte
DEF
1
OSTS1
Preliminary User's Manual U16898EJ1V0UD
DEF
1 RMCE OSCSEL1 OSCSEL0 RINGOSC
OSTS0
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