RL78/G15 CHAPTER 17 SELECTABLE POWER-ON-RESET CIRCUIT
R01UH0959EJ0110 Rev.1.10 Page 647 of 765
Mar 7, 2023
17.4 Cautions for Selectable Power-on-reset Circuit
In a system where the supply voltage (V
DD
) fluctuates for a certain period in the vicinity of the SPOR detection voltage
(V
SPOR
, V
SPDR
), the system may be repeatedly reset and released from the reset status. In this case, the time from
release of reset to the start of the operation of the microcontroller can be arbitrarily set by taking the following action.
<Action>
After releasing the reset signal, wait for the supply voltage fluctuation period of each system by means of a timer and
etc., and then initialize the ports.
Figure 17-3. Example of Software Processing When Supply Voltage Fluctuation is 50 ms or Less in Vicinity of
the Voltage Detection Level
No
Selectable power-on-reset
: f
CLK
= High-speed on-chip oscillator clock (16 MHz (MAX.))
Source: f
MCK
= (16 MHz (MAX.))/2
12
,
where comparison value = 195: ≅ 50 ms
Timer starts (TS0n = 1).
Reset
Initialization processing
<1>
Setting timer array unit
(to measure 50 ms)
Clearing WDT
50 ms has passed?
(TMIF0n = 1?)
Initialization processing
<2>
Yes
: Initial setting for port.
Setting of division ratio of system clock,
such as setting of timer or A/D converter.
Note 1
Note 1. If reset is generated again during this period, initialization processing <2> is not started.
Remark n: Channel number
For 8-pin and 10-pin products, n = 0, 1; for 16-pin products, n = 0 to 3, 5, and 7; and for 20-pin products, n = 0
to 7.
Figure 16-5 Example of Procedure for Checking Reset
in CHAPTER 16 RESET FUNCTION.
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