2-3
Seiko Epson Corporation
S1C31D50 TECHNICAL MANUAL
(Rev. 1.00)
2.1.4.
V
D1
Regulator Voltage Mode
The V
D1
regulator
s
upports two voltage modes, mode0 and mode1.
When the IC runs with a low-speed clock, setting the V
D1
regulator into mode1 reduces power
consumption.
When the voltage mode is switched, the system clock source automatically stops operating and it
resumes operating after the voltage has stabilized. Table 2.1.4.1 shows the stop period of the system
clock.
Table 2.1.4.1 System Clock Stop Period After Switching Voltage Mode
System clock
Stop period
IOSC
4,096 cycles
OSC1
Number of cycles set using the CLGOSC1.OSC1WT[1:0] bits
Procedure to switch from mode0 to mode1
1.
Set the MODEN bits of the peripheral circuits to 0.
(Stop using peripheral circuits)
2.
Write 0x0096 to the SYSPROT.PROT[15:0] bits.
(Remove system protection)
3.
Switch the system clock to a low-speed clock
(OSC1, IOSC 1.8 MHz or 0.9 MHz).
4.
Stop OSC3 and EXOSC.
5.
Configure the following PWGACTL register bits.
-
Set the PWGACTL.REGSEL bit to 0.
(Switch to mode1)
-
Set the PWGACTL.REGDIS bit to 1.
(Discharge)
-
Set the PWGACTL.REGMODE[1:0] bits to 0x2.
(Set to normal mode)
6.
Configure the following PWGACTL register bits after the system clock supply has resumed.
-
Set the PWGACTL.REGDIS bit to 0.
(Stop discharging)
-
Set the PWGACTL.REGMODE[1:0] bits to 0x0.
(Set to automatic mode)
7.
Write a value other than 0x0096 to the SYSPROT.PROT[15:0] bits.
(Set system protection)
Procedure to switch from mode1 to mode0
1.
Set the MODEN bits of the peripheral circuits to 0.
(Stop using peripheral circuits)
2.
Write 0x0096 to the SYSPROT.PROT[15:0] bits.
(Remove system protection)
3.
Configure the following PWGACTL register bits.
-
Set the PWGACTL.REGSEL bit to 1.
(Switch to mode0)
-
Set the PWGACTL.REGMODE[1:0] bits to 0x2.
(Set to normal mode)
4.
Set the PWGACTL.REGMODE[1:0] bits to 0x0after the system clock supply has resumed.
(Set to automatic mode)
5.
Switch the system clock to a high-speed clock.
6.
Write a value other than 0x0096 to the SYSPROT.PROT[15:0] bits.
(Set system protection)
Notes:
•
After the voltage mode has been switched, correct the RTC, as the RTC operating clock
is also stopped for the period set using the CLGOSC1.OSC1WT[1:0] bits.
•
Always use the IC in mode0 when V
DD
is 3.6 V or higher.
•
If you use two voltage mode, set mode1 before sleep or halt mode.
Summary of Contents for S1C31D50
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