NEC 78K0S/K 1+ Series Application Note page 9

Note 2. If the high-speed internal oscillation clock or an external clock input is selected as the system clock,
no oscillation stabilization time is required, so the setting becomes invalid (don't care).
Caution Bits 4 and 7 must be set to 1.
Remark x: don't care
[Example 1] The high-speed internal oscillation clock is used, used as the RESET pin, and the low-speed internal
oscillator can be stopped (same setting as the sample program).
Address: 0080H
1 x x
Note Stopping the low-speed internal oscillator oscillation, stopping watchdog timer operation, and setting the
clock frequency are performed after reset release. For details, refer to
Clock Setting.
The option byte setting value is
described together with the protect byte setting (hereinafter, writing to all blocks is enabled), the following results.
("x" is set to 0 in the example below.)
OPBT CSEG
DB
DB
To use C language, prepare an assembly language source file (file name: "*.asm (*: arbitrary)") such as the one
shown below, specify it as the project source file, and build it together with other source files (main.c).
OPBT CSEG
DB
DB
end
Remark The protect byte (address: 0081H) is used to set the prohibited areas for writing and block erasure
whose set contents are valid only during self programming. For details, refer to the user's manual of
each product (78K0S/KU1+, 78K0S/KY1+, 78K0S/KA1+, 78K0S/KB1+).
CHAPTER 4 SETTING METHODS
1 1 1 x
"1xx111x0 (x: don't care, bits 4 and 7 must be set to 1)". When the software is
AT 0080H
10011100B
11111111B
AT 0080H
10011100B
11111111B
Application Note U18752EJ2V0AN
0
Control of low-speed internal oscillator oscillation
Oscillation is stopped by software setting
0
(LSRSTOP bit is set to 1).
* In this sample program, the watchdog timer is not used.
Oscillation is therefore set so that it can be stopped by
software.
Selection of system clock source
1 x High-speed internal oscillation clock (8 MHz (TYP.))
Selection of P34/RESET pin function
1 Used as a RESET pin.
Specification of oscillation stabilization time on power
application or after reset release
(Crystal or ceramic oscillation is not used, so setting
x x
is invalid.)
4.4 Watchdog Timer Setting
Note
Note
and 4.5
9