2 POWER SUPPLY, RESET, AND CLOCKS
2-8
Seiko Epson Corporation
S1C17M12/M13 TECHNICAL MANUAL
(Rev. 1.2)
The setting values of the CLGOSC3.OSC3INV[1:0] and CLGOSC3.OSC3WT[2:0] bits should be determined
after performing evaluation using the populated circuit board.
Note: Make sure the CLGOSC.OSC3EN bit is set to 0 (while the OSC3 oscillation is halted) when
switching the oscillator within two types.
System clock switching
The CPU boots using IOSCCLK as SYSCLK. After booting, the clock source of SYSCLK can be switched ac-
cording to the processing speed required. The SYSCLK frequency can also be set by selecting the clock source
division ratio, this makes it possible to run the CPU at the most suitable performance for the process to be ex-
ecuted. The CLGSCLK.CLKSRC[1:0] and CLGSCLK.CLKDIV[1:0] bits are used for this control.
The CLGSCLK register bits are protected against writings by the system protect function, therefore, the system
protection must be removed by writing 0x0096 to the MSCPROT.PROT[15:0] bits before the register setting can
be altered. For the transition between the operating modes including the system clock switching, refer to “Oper-
ating Mode.”
Clock control in SLEEP mode
The CPU enters SLEEP mode when it executes the slp instruction. Whether the clock sources being operated
are stopped or not at this point can be selected in each source individually. This allows the CPU to fast switch
between SLEEP mode and RUN mode, and the peripheral circuits to continue operating without disabling the
clock in SLEEP mode. The CLGOSC.IOSCSLPC, CLGOSC.OSC3SLPC, and CLGOSC.EXOSCSLPC bits are
used for this control. Figure 2.3.4.3 shows a control example.
IOSCCLK
(Unstable)
OSC3CLK
(Unstable)
(1) When the CLGOSC.OSC3SLPC bit = 1
SYSCLK
(CPU operating clock)
SLEEP mode
(CPU stop, CLK stop)
Executing the
slp instruction
Interrupt
(Wake-up)
Oscillation stabilization waiting time
IOSCCLK
IOSCCLK
IOSCCLK
(Unstable)
LEDC
operating clock
(CLK stop)
∗
The LEDC stops operating in
SLEEP mode as the clock stops.
OSC3CLK
OSC3CLK
(2) When the CLGOSC.OSC3SLPC bit = 0
SYSCLK
(CPU operating clock)
SLEEP mode
(CPU stop, CLK stop)
Executing the
slp instruction
Interrupt
(Wake-up)
IOSCCLK
IOSCCLK
LEDC
operating clock
∗
The LEDC continues operating in
SLEEP mode as the clock is being supplied.
OSC3CLK
Figure 2.3.4.3 Clock Control Example in SLEEP Mode
The SYSCLK condition (clock source and division ratio) at wake-up from SLEEP mode to RUN mode can also
be configured. This allows flexible clock control according to the wake-up process. Configure the clock using
the CLGSCLK.WUPSRC[1:0] and CLGSCLK.WUPDIV[1:0] bits, and write 1 to the CLGSCLK.WUPMD bit
to enable this function.