Datasheet

CHAPTER 15 OPTION BYTE
User’s Manual U18172EJ3V0UD
222
15.2.2 μ PD78F950x
Figure 15-4. Format of Option Byte (
μ PD78F950x) (1/2)
Address: 0080H
7 6 5 4 3 2 1 0
1 1 1 ENPU34 RMCE OSCSEL1 OSCSEL0 LIOCP
ENPU34 Selection of on-chip pull-up resistor on RESET pin
1 On-chip pull-up resistor on RESET pin is selected.
0 On-chip pull-up resistor on RESET pin is not selected.
Remark When used as RESET pin, the pin can be left open by setting ENPU34 to "1".
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.
When used as an input-only port (P34), the setting of the on-chip pull-up resistor can be done
by PU34 on PU3 register.
OSCSEL1 OSCSEL0 Selection of system clock source
0 0 Setting prohibited
0 1 External clock input
1
×
High-speed internal oscillation clock
Caution Because the EXCLK pin is also used as the P23 pin, the condition under which the EXCLK
pin can be used differ depending on the selected system clock source.
(1) External clock input is selected
Because the pin is used as an external clock input pin, P23 cannot be used as an I/O port
pin.
(2) High-speed internal oscillation clock is selected
P23 pin can be used as an I/O port pin.
Remark × : don’t care
<R>