Chapter 20 Power-On-Clear Circuit; Functions Of Power-On-Clear Circuit - NEC 78K0 User Manual

20.1 Functions of Power-on-Clear Circuit

The power-on-clear circuit (POC) has the following functions.
• Generates internal reset signal at power on.
• Compares supply voltage (V
V .
POC
• The following can be selected by a mask option.
POC disabled
•
POC used (detection voltage: V
•
POC used (detection voltage: V
•
Note This option cannot be selected in (A1) and (A2) grade products because their supply voltage V
5.5 V.
Caution If an internal reset signal is generated in the POC circuit, the reset control flag register (RESF) is
cleared to 00H.
Remark This product incorporates multiple hardware functions that generate an internal reset signal. A flag that
indicates the reset cause is located in the reset control flag register (RESF) for when an internal reset
signal is generated by the watchdog timer (WDT), low-voltage-detection (LVI) circuit, or clock monitor.
RESF is not cleared to 00H and the flag is set to 1 when an internal reset signal is generated by WDT,
LVI, or the clock monitor.
For details of the RESF, refer to CHAPTER 18 RESET FUNCTION.

CHAPTER 20 POWER-ON-CLEAR CIRCUIT

) and detection voltage (V
DD
= 2.85 V ±0.15 V)
POC
= 3.5 V ±0.2 V)
POC
User's Manual U16227EJ2V0UD
), and generates internal reset signal when V
POC
Note
<
DD
is 3.3 to
DD
359