11 SUPPLY VOLTAGE DETECTOR (SVD3)
S1C31D50/D51 TECHNICAL MANUAL
Seiko Epson Corporation
11-3
(Rev. 2.00)
11.3.3 Clock Supply in DEBUG Mode
The CLK_SVD3 supply during DEBUG mode should be controlled using the SVD3CLK.DBRUN bit.
The CLK_SVD3 supply to SVD3 is suspended when the CPU enters DEBUG mode if the SVD3CLK.DBRUN bit
= 0. After the CPU returns to normal mode, the CLK_SVD3 supply resumes. Although SVD3 stops operating when
the CLK_SVD3 supply is suspended, the registers retain the status before DEBUG mode was entered.
If the SVD3CLK.DBRUN bit = 1, the CLK_SVD3 supply is not suspended and SVD3 will keep operating in DE-
BUG mode.
11.4 Operations
11.4.1 SVD3 Control
Starting detection
SVD3 should be initialized and activated with the procedure listed below.
1. Write 0x0096 to the MSCPROT.PROT[15:0] bits. (Remove system protection)
2. Configure the operating clock using the SVD3CLK.CLKSRC[1:0] and SVD3CLK.CLKDIV[2:0] bits.
3. Set the following SVD3CTL register bits:
- SVD3CTL.VDSEL and SVD3CTL.EXSEL bits (Select detection voltage (V
DD
, EXSVD0, or EXSVD1))
- SVD3CTL.SVDSC[1:0] bits
(Set low power supply voltage detection counter)
- SVD3CTL.SVDC[4:0] bits
(Set SVD detection voltage V
SVD
/EXSVD detection
voltage V
SVD_EXT
)
- SVD3CTL.SVDRE[3:0] bits
(Select reset/interrupt mode)
- SVD3CTL.SVDMD[1:0] bits
(Set intermittent operation mode)
4. Set the following bits when using the interrupt:
- Write 1 to the SVD3INTF.SVDIF bit.
(Clear interrupt flag)
- Set the SVD3INTE.SVDIE bit to 1.
(Enable SVD3 interrupt)
5. Set the SVD3CTL.MODEN bit to 1.
(Enable SVD3 detection)
6. Write a value other than 0x0096 to the MSCPROT.PROT[15:0] bits. (Set system protection)
Terminating detection
Follow the procedure shown below to stop SVD3 operation.
1. Write 0x0096 to the MSCPROT.PROT[15:0] bits. (Remove system protection)
2. Write 0 to the SVD3CTL.MODEN bit.
(Disable SVD3 detection)
3. Write a value other than 0x0096 to the MSCPROT.PROT[15:0] bits. (Set system protection)
Reading detection results
The following two detection results can be obtained by reading the SVD3INTF.SVDDT bit:
• When SVD3INTF.SVDDT bit = 0
Power supply voltage (V
DD
, EXSVD
n
)
≥
SVD detection voltage V
SVD
or EXSVD detection voltage V
SVD_EXT
• When SVD3INTF.SVDDT bit = 1
Power supply voltage (V
DD
, EXSVD
n
) < SVD detection voltage V
SVD
or EXSVD detection voltage V
SVD_EXT
Before reading the SVD3INTF.SVDDT bit, wait for at least SVD circuit enable response time after 1 is written
to the SVD3CTL.MODEN bit (refer to “Supply Voltage Detector Characteristics, SVD circuit enable response
time t
SVDEN
” in the “Electrical Characteristics” chapter).
After the SVD3CTL.SVDC[4:0] bits setting value is altered to change the SVD detection voltage V
SVD
/EXS-
VD detection voltage V
SVD_EXT
when the SVD3CTL.MODEN bit = 1, wait for at least SVD circuit response
time before reading the SVD3INTF.SVDDT bit (refer to “Supply Voltage Detector Characteristics, SVD circuit
response time t
SVD
” in the “Electrical Characteristics” chapter).