CHAPTER 15 OPTION BYTE
User’s Manual U18172EJ2V0UD
210
15.2 Format of Option Byte
Format of option bytes is shown below.
Figure 15-2. Format of Option Byte (1/2)
Address:
0080H
7 6 5 4 3 2 1 0
1
DEFOSTS1
DEFOSTS0
1 RMCE
OSCSEL1
OSCSEL0
LIOCP
DEFOSTS1
DEFOSTS0
Oscillation stabilization time on power application or after reset release
0 0
2
10
/fx (102.4
µ
s)
0 1
2
12
/fx (409.6
µ
s)
1 0
2
15
/fx (3.27 ms)
1 1
2
17
/fx (13.1 ms)
Caution The setting of this option is valid only when the crystal/ceramic oscillation clock is selected
as the system clock source. No wait time elapses if the high-speed internal oscillation clock
or external clock input is selected as the system clock source.
RMCE
Control of RESET pin
1
RESET pin is used as is.
0
RESET pin is used as input port pin (P34).
Caution Because the option byte is referenced after reset release, if a low level is input to the RESET
pin before the option byte is referenced, then the reset state is not released.
Also, when setting 0 to RMCE, connect the pull-up resistor.
OSCSEL1 OSCSEL0
Selection
of system clock source
0 0
Crystal/ceramic
oscillation
clock
0 1
External
clock
input
1
×
High-speed internal oscillation clock
Caution Because the X1 and X2 pins are also used as the P23/ANI3 and P22/ANI2 pins, the conditions
under which the X1 and X2 pins can be used differ depending on the selected system clock
source.
(1) Crystal/ceramic oscillation clock is selected
The X1 and X2 pins cannot be used as I/O port pins or analog input pins of A/D converter
because they are used as clock input pins.
(2) External clock input is selected
Because the X1 pin is used as an external clock input pin, P23/ANI3 cannot be used as
an I/O port pin or an analog input pin of A/D converter.
(3) High-speed internal oscillation clock is selected
P23/ANI3 and P22/ANI2 pins can be used as I/O port pins or analog input pins of A/D
converter.
Remark
×
: don’t care