Datasheet

78K0/Ix2 CHAPTER 24 OPTION BYTE
R01UH0010EJ0500 Rev.5.00 646
Feb 28, 2012
CHAPTER 24 OPTION BYTE
24.1 Functions of Option Bytes
The flash memory at 0080H to 0084H of the 78K0/Ix2 microcontrollers is an option byte area. When power is turned on
or when the device is restarted from the reset status, the device automatically references the option bytes and sets
specified functions. When using the product, be sure to set the following functions by using the option bytes.
When the boot swap operation is used during self-programming, 0080H to 0084H are switched to 1080H to 1084H.
Therefore, set values that are the same as those of 0080H to 0084H to 1080H to 1084H in advance.
(1) 0080H/1080H
Internal low-speed oscillator operation
Can be stopped by software
Cannot be stopped
Watchdog timer interval time setting
Watchdog timer counter operation
Enabled counter operation
Disabled counter operation
Watchdog timer window open period setting
Caution Set a value that is the same as that of 0080H to 1080H because 0080H and 1080H are switched
during the boot swap operation.
(2) 0081H/1081H
LVI default start operation control
During LVI default start function enabled (LVISTART = 1)
The device is in the reset state after reset release or upon power application and until the supply voltage reaches
1.91 V (TYP.). It is released from the reset state when the voltage exceeds 1.91 V (TYP.).
If the supply voltage rises to 2.7 V after reset release or power application at a rate slower than 0.5 V/ms (MIN.),
LVI default start function operation is recommended.
During LVI default start function stopped (LVISTART = 0)
The device is in the reset state after reset release or upon power application and until the supply voltage reaches
1.61 V (TYP.). It is released from the reset state when the voltage exceeds 1.61 V (TYP.).
Caution LVISTART can only be written by using a dedicated flash memory programmer. It cannot be set
or change during self-programming or boot swap operation during self-programming.