Datasheet

78K0/Kx2-L CHAPTER 21 POWER-ON-CLEAR CIRCUIT
R01UH0028EJ0400 Rev.4.00 665
Sep 27, 2010
CHAPTER 21 POWER-ON-CLEAR CIRCUIT
21.1 Functions of Power-on-Clear Circuit
The power-on-clear circuit (POC) is mounted onto all 78K0/Kx2-L microcontroller products.
The power-on-clear circuit has the following functions.
• Generates internal reset signal at power on.
• The reset signal is released when the supply voltage (V
DD) exceeds POC detection voltage (VPOR = 1.61 V ±0.09 V).
Caution If the LVI default function enabled is set by using an option byte, the reset signal is not released
until the supply voltage (V
DD) exceeds 1.91 V ±0.1 V.
• Compares supply voltage (V
DD) and POC detection voltage (VPDR = 1.59 V ±0.09 V), generates internal reset signal
when V
DD < VPDR.
Caution If an internal reset signal is generated in the POC circuit, the reset control flag register (RESF) is
cleared to 00H.
Remark The 78K0/Kx2-L microcontrollers incorporate multiple hardware functions that generate an internal reset
signal. A flag that indicates the reset source is located in the reset control flag register (RESF) for when
an internal reset signal is generated by the watchdog timer (WDT) and low-voltage-detector (LVI). RESF
is not cleared to 00H and the flag is set to 1 when an internal reset signal is generated by WDT or LVI.
For details of RESF, refer to CHAPTER 20 RESET FUNCTION.