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16.4 Cautions for Power-on-Clear Circuit
In a system where the supply voltage (V
voltage (V
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
software counter that uses a timer, and then initialize the ports.
• If supply voltage fluctuation is 50 ms or less in vicinity of POC detection voltage
Note 1
Notes 1.
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CHAPTER 16 POWER-ON-CLEAR CIRCUIT
), the system may be repeatedly reset and released from the reset status. In this case, the time from
POC
Figure 16-3. Example of Software Processing After Reset Release (1/2)
Reset
Initialization
processing <1>
Power-on-clear
Setting 8-bit timer H1
(to measure 50 ms)
Clearing WDT
No
50 ms has passed?
(TMIFH1 = 1?)
Yes
Initialization
processing <2>
If reset is generated again during this period, initialization processing <2> is not started.
2.
A flowchart is shown on the next page.
) fluctuates for a certain period in the vicinity of the POC detection
DD
;
Check the reset source
Initialize the port.
; f
= Internal low-speed oscillation clock (264 kHz (MAX.)) (default)
RL
Source: f
(264 kHz (MAX.))/2
RL
where comparison value = 104: ≅ 50 ms
Timer starts (TMHE1 = 1).
; Setting of division ratio of system clock,
such as setting of timer
Preliminary User's Manual U19014EJ1V0UD
Note 2
7
,
433
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