Cautions For Power-On-Clear Circuit - NEC 78K0S/KA1+ User Manual

15.4 Cautions for Power-on-Clear Circuit

In a system where the supply voltage (V
voltage (V ), the system may be repeatedly reset and released from the reset status. In this case, the time from
POC
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.
Figure 15-3. Example of Software Processing After Release of Reset (1/2)
• If supply voltage fluctuation is 50 ms or less in vicinity of POC detection voltage
processing <1>
Setting 8-bit timer H1
(50 ms
Note 1
No
50 ms has passed?
Notes 1. If reset is generated again during this period, initialization processing <2> is not started.
2. A flowchart is shown on the next page.
CHAPTER 15 POWER-ON-CLEAR CIRCUIT
) fluctuates for a certain period in the vicinity of the POC detection
DD
Reset
; Check reset source
Initialization
Initialization of ports
Setting WDT
Power-on clear
; f
Source : f
is measured)
Timer starts (TMHE1 = 1)
Clears WDT
(TMIFH1 = 1?)
Yes
; Specify the division ratio of the system clock,
Initialization
setting Timaer, setting A/D Converter, etc.
processing <2>
User's Manual U16898EJ3V0UD
Note 2
= High-speed internal oscillation clock (8.4 MHz (MAX.)) /2
XP
(2.1 MHz (MAX.)) /2 12
RL
51 ms when the compare value is 25
2
(default value)
,
247