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EPSON
S1C6F567 TECHNICAL MANUAL
CHAPTER 4: PERIPHERAL CIRCUITS AND OPERATION (SVD Circuit)
4.13 SVD (Supply Voltage Detection) Circuit
4.13.1 Configuration of SVD circuit
The S1C6F567 has a built-in SVD (supply voltage detection) circuit, so that the software can find when
the source voltage lowers. It is possible to check an external voltage drop, other than the supply voltage.
Turning the SVD circuit ON/OFF and the SVD criteria voltage setting can be done with software.
Figure 4.13.1.1 shows the configuration of the SVD circuit.
V
Detection output
Data
bus
DD
VSS
SVDON
SVDS3
|
SVDS0
Criteria voltage
setting circuit
SVD circuit
SVDDT
SVD
terminal
Fig. 4.13.1.1 Configuration of SVD circuit
4.13.2 Mask option
Besides the supply voltage (VDD terminal–VSS terminal) drop detection, the SVD circuit can detect the
external voltage (SVD terminal–VSS terminal) input from the SVD terminal by comparing it with the
detected voltage (1.05 V). In the mask ROM model, this function can be enabled or disabled by mask
option. In the S1C6F567, this function cannot be disabled.
4.13.3 SVD operation
The SVD circuit compares the criteria voltage set by software and the supply voltage (VDD terminal–VSS
terminal) or the external voltage (SVD terminal–VSS terminal) and sets the results into the SVDDT latch.
By reading the data of this SVDDT latch, it can be determined by means of software whether the supply
voltage is normal or has dropped.
The criteria voltage can be set by the SVDS3–SVDS0 registers as shown in Table 4.13.3.1.
When "0" is written to the SVDS3–SVDS0 register, the SVD circuit does not compare the supply voltage
(VDD terminal–VSS terminal) but compares between the external voltage (SVD terminal–VSS terminal)
input from the SVD terminal and 1.05 V.
Table 4.13.3.1 Criteria voltage setting
SVDS3
0
SVDS2
1
0
SVDS1
1
0
1
0
SVDS0
1
0
1
0
1
0
1
0
Criteria
voltage (V)
–
1.05 (external)
SVDS3
1
SVDS2
1
0
SVDS1
1
0
1
0
SVDS0
1
0
1
0
1
0
1
0
Criteria
voltage (V)
3.30
3.20
3.10
3.00
2.90
2.80
–
If the criteria voltage is set to 2.7 V or less (SVDS = 9–1), the SVD operation cannot be guaranteed since
the lower limit of the operating voltage range in the S1C6F567 is 2.7 V. Furthermore, the detected voltage
may be less than 2.7 V due to error even if the criteria voltage is set to 2.8 V. In this case operation cannot
be guaranteed. Refer to Chapter 9, "Electrical Characteristics", for the SVD circuit characteristics.