User’s Manual U16898EJ3V0UD
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CHAPTER 17 OPTION BYTE
17.1 Functions of Option Byte
The address 0080H of the flash memory of the 78K0S/KA1+ is an option byte area. When power is supplied or
when starting after a reset, the option byte is automatically referenced, and settings for the specified functions are
performed. When using the product, be sure to set the following functions by using the option byte.
(1) Selection of system clock source
•
High-speed internal oscillation clock
•
Crystal/ceramic oscillation clock
•
External clock input
(2) Low-speed internal oscillation clock oscillation
•
Cannot be stopped.
•
Can be stopped by software.
(3) Control of RESET pin
•
Used as RESET pin
•
RESET pin is used as an input port pin (P34).
(4) Oscillation stabilization time on power application or after reset release
•
2
10
/f
X
•
2
12
/f
X
•
2
15
/f
X
•
2
17
/f
X
Figure 17-1. Positioning of Option Byte
Option byte
OSCSEL1
RMCE
1
1
Flash memory
2048/4096
×
8 bits)
07FFH/0FFFH
0000H
0080H
DEF
OSTS1
OSCSEL0 LIOCP
DEF
OSTS0