2 POWER SUPPLY, RESET, AND CLOCKS
S1C17F13 TeChniCal Manual
Seiko epson Corporation
2-5
(Rev. 1.0)
Clock Generator (CLG)
2.3
Overview
2.3.1
CLG is the clock generator that controls the clock sources and manages clock supply to the CPU and the peripheral
circuits. The main features of CLG are outlined below.
• Supports multiple clock sources.
- OSC3B oscillator circuit that oscillates with a fast startup and no external parts required
- Low-power OSC1B oscillator circuit that oscillates with no external parts required
- High-precision and low-power OSC1A oscillator circuit that uses a 32.768 kHz crystal resonator
- OSC3A oscillator circuit that supports high-speed crystal and ceramic resonators up to 20 MHz
- EXOSC clock input circuit that allows input of square wave and sine wave clock signals
• The system clock (SYSCLK), which is used as the operating clock for the CPU and bus, and the peripheral cir-
cuit operating clocks can be configured individually by selecting the suitable clock source and division ratio.
• OSC3BCLK output from the OSC3B oscillator circuit is used as the boot clock for fast booting.
• Controls the oscillator and clock input circuits to enable/disable according to the operating mode, RUN or
SLEEP mode.
• Provides a flexible system clock switching function at SLEEP mode cancelation.
- The clock sources to be stopped in SLEEP mode can be selected.
- SYSCLK to be used at SLEEP mode cancelation can be selected from all clock sources (OSC3B, OSC3A,
and EXOSC).
- The oscillator and clock input circuit on/off state can be maintained or changed at SLEEP mode cancelation.
• Provides the FOUT function to output an internal clock for driving external ICs or for monitoring the internal
state.
Figure 2.3.1.1 shows the CLG configuration.
CLG
Inter
nal data
bu
s
OSC1BCLK
SYSCLK
SLEEP, WAKEUP
OSC1
OSC2
EXOSC
FOUT
OSC1EN
OSC1SEL
CLKSRC[1:0]
CLKDIV[1:0]
WUPMD
CLKSRC[
x
:0]
CLKDIV[
x
:0]
WUPSRC[1:0]
WUPDIV[1:0]
FOUTDIV[2:0]
OSC1B
oscillator
circuit
Divider
Clock
selector
System
clock
controller
OSC1ACLK
F1 (1 [Hz])
F256 (1/256 [Hz])
OSC1CLK
X’tal1
OSC3BCLK
OSC3BEN
OSC3B
oscillator
circuit
OSC1A
oscillator
circuit
Divider
OSC3ACLK
OSC3AEN
OSC3A
oscillator
circuit
Divider
Divider
EXOSCCLK
EXOSCEN
EXOSC
clock input
circuit
FOUTEN
EXOSC
clock input
circuit
Clock
selector
Peripheral circuit 1
CLKSRC[
x
:0]
CLKDIV[
x
:0]
Clock
selector
Peripheral circuit
n
To CPU and bus
To some
peripheral circuits
OSC3
OSC4
X’tal3/Ceramic3
Theoretical regulation
RTC reset
3.1.1 CLG Configuration
Figure 2.