10 SUPPLY VOLTAGE DETECTOR (SVD3)
S1C17M20/M21/M22/M23/M24/M25
Seiko Epson Corporation
10-5
TECHNICAL MANUAL (Rev. 1.0)
Once the SVDINTF.SVDIF bit is set, it will not be cleared even if the power supply voltage subsequently returns
to a value exceeding the SVD detection voltage V
SVD
/EXSVD detection voltage V
SVD_EXT
. An interrupt may occur
due to a temporary power supply voltage drop, check the power supply voltage status by reading the SVDINTF.
SVDDT bit in the interrupt handler routine.
10.5.2 SVD3 Reset
Setting the SVDCTL.SVDRE[3:0] bits to 0xa allows use of the SVD3 reset issuance function.
The reset issuing timing is the same as that of the SVDINTF.SVDIF bit being set when a low voltage is detected.
After a reset has been issued, SVD3 enters continuous operation mode even if it was operating in intermittent op-
eration mode, and continues operating. Issuing an SVD3 reset initializes the port assignment. However, when EXS-
VD0/1 is being detected, the input of the port for the EXSVD0/1 pin is sent to SVD3 so that SVD3 will continue
the EXSVD0/1 detection operation.
If the power supply voltage reverts to the normal level, the SVDINTF.SVDDT bit goes 0 and the reset state is can-
celed. After that, SVD3 resumes operating in the operation mode set previously via the initialization routine.
During reset state, the SVD3 control bits are set as shown in Table 10.5.2.1.
Table 10.5.2.1 SVD3 Control Bits During Reset State
Control register
Control bit
Setting
SVDCLK
DBRUN
Reset to the initial values.
CLKDIV[2:0]
CLKSRC[1:0]
SVDCTL
VDSEL
The set value is retained.
SVDSC[1:0]
Cleared to 0. (The set value becomes invalid as SVD3
enters continuous operation mode.)
SVDC[4:0]
The set value is retained.
SVDRE[3:0]
The set value (0xa) is retained.
EXSEL
The set value is retained.
SVDMD[1:0]
Cleared to 0 to set continuous operation mode.
MODEN
The set value (1) is retained.
SVDINTF
SVDIF
The status (1) before being reset is retained.
SVDINTE
SVDIE
Cleared to 0.
10.6 Control Registers
SVD3 Clock Control Register
Register name
Bit
Bit name
Initial
Reset
R/W
Remarks
SVDCLK
15–9 –
0x00
–
R
–
8
DBRUN
1
H0
R/WP
7
–
0
–
R
6–4 CLKDIV[2:0]
0x0
H0
R/WP
3–2 –
0x0
–
R
1–0 CLKSRC[1:0]
0x0
H0
R/WP
Bits 15–9 Reserved
Bit 8
DBRUN
This bit sets whether the SVD3 operating clock is supplied in DEBUG mode or not.
1 (R/WP): Clock supplied in DEBUG mode
0 (R/WP): No clock supplied in DEBUG mode
Bit 7
Reserved
Bits 6–4
CLKDIV[2:0]
These bits select the division ratio of the SVD3 operating clock.
Bits 3–2
Reserved
Bits 1–0
CLKSRC[1:0]
These bits select the clock source of SVD3.