R01UH0136EJ0210 Rev.2.10
Page 73 of 800
Jul 31, 2012
M16C/64A Group
7. Voltage Detector
7.4
Operations
7.4.1
Digital Filter
A digital filter can be used to monitor VCC1 input voltage. For the voltage detector i (i = 1 to 2), the
digital filter is enabled when the VWiC1 bit in the VWiC register is set to 0 (digital filter enabled).
fOCO-S divided by 1, 2, 4, or 8 is selected as a sampling clock. When using the digital filter, set the
CM14 bit in the CM1 register to 0 (125 kHz on-chip oscillator on).
The VCC1 input level is sampled by the digital filter for every sampling clock. When the same sampled
level is detected twice in a row, at the next sampling timing, the internal reset signal goes low or a
voltage monitor i interrupt request is generated. Therefore, when the digital filter is used, the time from
when the VCC1 input voltage level passes Vdeti until when a reset or an interrupt is generated is up to
three cycles of the sampling clock.
Since fOCO-S stops in stop mode, the digital filter does not function. When using voltage detector i to
exit stop mode, set the VWiC1 bit in the VWiC register to 1 (digital filter disabled).
Figure 7.2 shows Digital Filter Operation Example.
Figure 7.2
Digital Filter Operation Example
The above diagram assumes the following:
•
The VW12E bit in the VWCE register is 1 (voltage monitors 1 and 2 enabled).
•
The VW1C0 bit in the VW1C register is 1 (voltage monitor 1 interrupt/reset enabled).
•
The VW1C1 bit in the VW1C register is 0 (digital filter enabled).
•
The VW1C6 bit in the VW1C register is 0 (voltage monitor 1 interrupt at Vdet1 passage).
VCC1
Vdet1
Digital filter
sampling timer
VW1C2 bit in
the VW1C register
Internal signal
(Voltage monitor 1
interrupt request)
Up to 3 cycles of the sampling clock
Set to 0
VW1C3 bit in
the VW1C register
Up to 3 cycles of the sampling clock
Содержание M16C/60 Series
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