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This chapter describes how to set the option byte, vector table, stack pointer, watchdog timer, clock frequency, and
ports, as well as the main processing.
For how to set registers, refer to the user's manual of each product (78K0S/KU1+, 78K0S/KY1+, 78K0S/KA1+,
78K0S/KB1+).
For assembler instructions, refer to the
4.1
Option Byte Setting
The option byte must be set. The following items are set with the option byte.
(1) Selection of system clock source
(2) Control of low-speed internal oscillator oscillation
(3) Selection of P34/RESET pin function
(4) Specification of oscillation stabilization time on power application or after reset release (only when using crystal
or ceramic oscillation)
In this sample program, the option byte is set as described in
Address: 0080H
1
DEFOS
DEFOS
1
TS1
TS0
Note 1. 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
Setting
(Note 2, Caution, and Remark are on the next page.)
8
CHAPTER 4 SETTING METHODS
78K/0S Series Instructions User's
Figure 4-1. Option Byte Format
RMCE OSCSE
OSCSE
L1
L0
and
4.5 Clock
Setting.
Application Note U18752EJ2V0AN
Manual.
[Example
1], mentioned later.
LIOCP
Control of low-speed internal oscillator oscillation
Oscillation is stopped by software setting
0
(LSRSTOP bit is set to 1).
1
Cannot be stopped.
Selection of system clock source
0
0
Crystal or ceramic oscillation clock (10 MHz (MAX.))
0
1
External clock input (10 MHz (MAX.))
1
x
High-speed internal oscillation clock (8 MHz (TYP.))
Selection of P34/RESET pin function
0
Used as P34 (dedicated input port).
1
Used as a RESET pin.
Specification of oscillation stabilization time on power
application or after reset release
10
0
0
2
/fx
12
0
1
2
/fx
15
1
0
2
/fx
17
1
1
2
/fx
Note 1
Note 1
Note 2
4.4 Watchdog Timer
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