Datasheet

User’s Manual U18172EJ3V0UD
218
CHAPTER 15 OPTION BYTE
15.1 Functions of Option Byte
The address 0080H of the flash memory of the 78K0S/KU1+ 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.
15.1.1
μ PD78F920x
(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) (refer to 15.3 Caution When the RESET Pin Is Used as an
Input-Only Port Pin (P34)).
(4) Oscillation stabilization time on power application or after reset release
• 2
10
/fX
• 2
12
/fX
• 2
15
/fX
• 2
17
/fX
Figure 15-1. Positioning of Option Byte (
μ PD78F920x)
Option byte
OSCSEL1 RMCE11
Flash memory
(1024/2048/4096 × 8 bits)
03FFH/
07FFH/
0FFFH
0000H
0080H
DEF
OSTS1
OSCSEL0 LIOSP
DEF
OSTS0