26 SuPPlY VOlTaGe DeTeCTOR (SVD)
26-2
Seiko epson Corporation
S1C17624/604/622/602/621 TeChniCal Manual
Comparison Voltage Setting
26.3
The SVD circuit compares the power supply voltage (V
DD
) against the comparison voltage set by software and out-
puts results indicating whether the power supply voltage exceeds this comparison voltage. The comparison voltage
can be selected from among the 15 levels listed in Table 26.3.1 with the SVDC[3:0]/SVD_CMP register.
3.1 Comparison Voltage Settings
Table 26.
SVDC[3:0]
Comparison voltage
0xf
3.2 V
0xe
3.1 V
0xd
3.0 V
0xc
2.9 V
0xb
2.8 V
0xa
2.7 V
0x9
2.6 V
0x8
2.5 V
0x7
2.4 V
0x6
2.3 V
0x5
2.2 V
0x4
2.1 V
0x3
2.0 V
0x2
1.9 V
0x1
1.8 V
0x0
Reserved
(Default: 0x0)
SVD Control
26.4
Power supply voltage detection using the SVD circuit is initiated by writing 1 to SVDEN/SVD_EN register and is
stopped by writing 0.
The results can be read out from the SVDDT/SVD_RSLT register.
The detection results and SVDDT readings are as follows.
• When power supply voltage (V
DD
)
≥
comparison voltage: SVDDT = 0
• When power supply voltage (V
DD
) < comparison voltage: SVDDT = 1
When SVD interrupts are enabled and SVDEN is set to 1, an interrupt occurs as soon as the power supply voltage
drops below the comparison voltage, and the detection result becomes 1. This interrupt can be used to indicate bat-
tery depletion and to initiate the heavy load protection function. See the following section for more information on
interrupt control.
Note that if a temporary voltage drop causes an interrupt, the interrupt will not be cleared even when the voltage
subsequently returns to a value exceeding the comparison voltage. The SVDDT should be checked in the interrupt
handler routine.
notes: • An SVD circuit-enable response time is required to obtain stable detection results after
SVDEN is altered from 0 to 1. Also when SVDC[3:0] is altered, an SVD circuit response time
is required to obtain stable detection results. For these response times, see “Electrical Char-
acteristics.”
• Operating the SVD circuit increases current consumption. If power supply voltage detection is
not required, stop SVD operations by setting SVDEN to 0.
SVD interrupt
26.5
The SVD module includes a function for generating interrupts when power supply voltage drops are detected.
Power supply voltage drop detection interrupt
This cause of interrupt is generated when the power supply voltage (V
DD
) detected value drops below the com-
parison voltage while SVD is operating (SVDEN = 1). It sets the interrupt flag SVDIF/SVD_IFLG register in
the SVD module to 1. Once set, SVDIF is not reset even if the power supply voltage subsequently returns to a
value exceeding the comparison voltage. SVDIF is reset to 0 by writing 1.