Appendix B Power Saving; Operating Status Configuration Examples For Power Saving - Epson S1C17M12 Technical Manual

Appendix B Power Saving

Current consumption will vary dramatically, depending on CPU operating mode, operation clock frequency, periph-
eral circuits being operated, and power generator operating mode. Listed below are the control methods for saving
power.
B.1 Operating Status Configuration Examples for Power Saving
Table B.1.1 lists typical examples of operating status configuration with consideration given to power saving.
Operating status
configuration
Standby
Peripheral circuit operations
High-speed processing
If the current consumption order by the operating status configuration shown in Table B.1.1 is different from one
that is listed in "Electrical Characteristics," check the settings shown below.
PWGVD1CTL.REGMODE[1:0] bits of the power generator
If the PWGVD1CTL.REGMODE[1:0] bits of the power generator is 0x2 (normal mode) when the CPU enters
SLEEP mode, current consumption in SLEEP mode will be larger than I
teristics." Set the PWGVD1CTL.REGMODE[1:0] bits to 0x3 (economy mode) or 0x0 (automatic mode) before
executing the slp instruction.
CLGOSC.IOSCSLPC/OSC3SLPC/EXOSCSLPC bits of the clock generator
Setting the CLGOSC.IOSCSLPC, OSC3SLPC, or EXOSCSLPC bit of the clock generator to 0 disables the
oscillator circuit stop control when the slp instruction is executed. To stop the oscillator circuits during SLEEP
mode, set these bits to 1.
MODEN bits of the peripheral circuits
Setting the MODEN bit of each peripheral circuit to 1 starts supplying the operating clock enabling the periph-
eral circuit to operate. To reduce current consumption, set the MODEN bits of unnecessary peripheral circuits
to 0. Note that the real-time clock has no MODEN bit, therefore, current consumption does not vary if it is
counting or idle.
OSC3 (crystal/ceramic) oscillator circuit configurations
The OSC3 (crystal/ceramic) oscillator circuit provides some configuration items to support various crystal and
ceramic resonators. These configurations trade off current consumption for performance as shown below.
• The lower oscillation inverter gain setting (CLGOSC3.OSC3INV[1:0] bits) decreases current consumption.
• Using lower OSC3 external gate and drain capacitances decreases current consumption.
• Using a resonator with lower C
However, these configurations may reduce the oscillation margin and increase the frequency error, therefore, be
sure to perform matching evaluation using the actual printed circuit board.
S1C17M12/M13 TECHNICAL MANUAL
(Rev. 1.2)
Table B.1.1 Typical Operating Status Configuration Examples
Current IOSC/OSC3/
V
D1
consumption
Low
Economy
↑
Normal
↓
High
value decreases current consumption.
L
Seiko Epson Corporation
CPU
EXOSC
OFF SLEEP
SLEEP or HALT
ON
IOSC/OSC3/EXOSC RUN
SLP
APPENDIX B POWER SAVING
Current consumption listed in
electrical characteristics
I
SLP
I
HALT1
I
RUN1
that is listed in "Electrical Charac-
AP-B-1