PD17012_15 Datasheet, PDF (289/320 Pages) Renesas Technology Corp – 4-BIT SINGLE-CHIP MICROCONTROLLERS WITH DIGITAL TUNING SYSTEM HARDWARE

µPD17012, 17P012
Example of operation
VDD ^{5 V}
0V
H
CE
L
5 ms pulse
50 ms pulse
Basic timer 0 carry ^H
FF setting pulse L
50 ms
5 ms
50 ms
<1>
<4>
<2> Power failure detection
If processing time of <1> + <4> is
longer than 100 ms, CE reset is effected
in middle of processing <4>.
<1>
<3>
<2> Power failure detection
If processing time of <1> + <3>
is too long, CE reset is effected.
CE reset
<5>
CE reset
CE reset may be effected immediately depending
on when basic timer 0 carry FF setting time is changed.
Therefore, if <5> is executed before <4>,
power failure processing <4> may not be
completely executed.
22.6.3 Power failure detection by RAM judgement method
The RAM judgement method is to detect a power failure by judging whether the contents of the data memory
at a specific address are the specified value.
An example of a program that detects a power failure by the RAM judgement method is shown below.
The RAM judgement method detects a power failure by comparing an undefined value with the specified value
because the contents of the data memory are undefined on application of supply voltage VDD.
Therefore, there is a possibility that a wrong judgment may be made as explained in 22.6.4 Notes on
detecting power failure by RAM judgement method.
Data Sheet U10101EJ4V0DS
287