UPD78F9234MC-5A4-A Datasheet, PDF (271/419 Pages) Renesas Technology Corp – Old Company Name in Catalogs and Other Documents

CHAPTER 18 OPTION BYTE
18.1 Functions of Option Byte
The address 0080H of the flash memory of the 78K0S/KB1+ 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) (refer to 18.3 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
• 2¹⁰/fX
• 2¹²/fX
• 2¹⁵/fX
• 2¹⁷/fX
0FFFH/1FFFH
Figure 18-1. Positioning of Option Byte
Flash memory
(4096/8192 × 8 bits)
0080H
0000H
Option byte
1
DEF DEF
OSTS1 OSTS0
1
RMCE OSCSEL1 OSCSEL0 LIOCP
User’s Manual U17446EJ5V0UD
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