Epson S1C63558 - Manual (Page 120)

110 EPSON S1C63558 TECHNICAL MANUAL
CHAPTER 4: PERIPHERAL CIRCUITS AND OPERATION (SVD Circuit)
When the SVDON register is set to "1", source voltage or external voltage detection by the SVD circuit is
executed. As soon as the SVDON register is reset to "0", the result is loaded to the SVDDT latch and the
SVD circuit goes OFF.
To obtain a stable detection result, the SVD circuit must be ON for at least l00 µsec. So, to obtain the SVD
detection result, follow the programming sequence below.
1. Set SVDON to "1"
2. Maintain for 100 µsec minimum
3. Set SVDON to "0"
4. Read SVDDT
When the SVD circuit is ON, the IC draws a large current, so keep the SVD circuit off unless it is.
4.13.4 I/O memory of SVD circuit
Table 4.13.4.1 shows the I/O addresses and the control bits for the SVD circuit.
Table 4.13.4.1 Control bits of SVD circuit
Address Comment
D3 D2
Register
D1 D0 Name Init
∗ 1 1 0
FF05H
0 0 SVDDT SVDON
R R/W
0
∗ 3
0 ∗ 3
SVDDT
SVDON
–
∗ 2
– ∗ 2
0
0
Low
On
Normal
Off
Unused
Unused
SVD evaluation data
SVD circuit On/Off
FF04H
SVDS3 SVDS2 SVDS1 SVDS0
R/W
SVDS3
SVDS2
SVDS1
SVDS0
0
0
0
0
SVD criteria voltage setting
0
2.20/1.05
8
2.60
1
2.20
9
2.70
2
2.20
10
2.80
3
2.20
11
2.90
4
2.20
12
3.00
5
2.30
13
3.10
6
2.40
14
3.20
7
2.50
15
3.30
[SVDS3–0]
Voltage(V)
[SVDS3–0]
Voltage(V)
*1 Initial value at initial reset
*2 Not set in the circuit
*3 Constantly "0" when being read
SVDS3–SVDS0: SVD criteria voltage setting register (FF04H)
Criteria voltage for SVD is set as shown in Table 4.13.3.1.
At initial reset, this register is set to "0".
SVDON: SVD control (ON/OFF) register (FF05H•D0)
Turns the SVD circuit ON and OFF.
When "1" is written: SVD circuit ON
When "0" is written: SVD circuit OFF
Reading: Valid
When the SVDON register is set to "1", a source voltage detection is executed by the SVD circuit. As soon
as SVDON is reset to "0", the result is loaded to the SVDDT latch. To obtain a stable detection result, the
SVD circuit must be ON for at least l00 µsec.
At initial reset, this register is set to "0".
SVDDT: SVD data (FF05H•D1)
This is the result of supply voltage detection.
When "0" is read: Supply voltage (V DD –V SS )
≥
Criteria voltage
When "1" is read: Supply voltage (V DD –V SS ) < Criteria voltage
Writing: Invalid
The result of supply voltage detection at time of SVDON is set to "0" can be read from this latch.
At initial reset, SVDDT is set to "0".