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ManualsBrandsRENESAS ManualsMicrocontrollers, Microprocessors & QuartzesEmbedded microcontroller LQFP 44 (10x10) 16-Bit 24 MHz I/O number 29
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RL78/L12 CHAPTER 21 POWER-ON-RESET CIRCUIT
R01UH0330EJ0200 Rev.2.00 754
Dec 13, 2013
CHAPTER 21 POWER-ON-RESET CIRCUIT
21.1 Functions of Power-on-reset Circuit
The power-on-reset circuit (POR) has the following functions.
• Generates internal reset signal at power on.
The reset signal is released when the supply voltage (V
DD) exceeds the detection voltage (VPOR). Note that the reset
state must be retained until the operating voltage becomes in the range defined in 30.4 or 31.4 AC Characteristics.
This is done by utilizing the voltage detection circuit or controlling the externally input reset signal.
• Compares supply voltage (V
DD) and detection voltage (VPDR), generates internal reset signal when VDD < VPDR. Note
that, after power is supplied, this LSI should be placed in the STOP mode, or in the reset state by utilizing the
voltage detection circuit or externally input reset signal, before the operation voltage falls below the range defined in
30.4 or 31.4 AC Characteristics. When restarting the operation, make sure that the operation voltage has returned
within the range of operation.
Caution If an internal reset signal is generated in the power-on-reset circuit, the reset control flag register
(RESF) is cleared.
Remarks 1. The RL78 microcontroller incorporates 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), voltage-detector (LVD), illegal
instruction execution, RAM parity error, or illegal-memory access. The RESF register is not cleared to
00H and the flag is set to 1 when an internal reset signal is generated by the watchdog timer (WDT),
voltage-detector (LVD), illegal instruction execution, RAM parity error, or illegal-memory access.
For details of the RESF register, see CHAPTER 20 RESET FUNCTION.
2. V
POR: POR power supply rise detection voltage
V
PDR: POR power supply fall detection voltage
For details, see 30.6.3 or 31.6.3 POR circuit characteristics.
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