Datasheet

CHAPTER 15 OPTION BYTE
User’s Manual U18172EJ3V0UD
220
15.2 Format of Option Byte
Format of option bytes is shown below.
15.2.1
μ PD78F920x
Figure 15-3. Format of Option Byte (
μ PD78F920x) (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