2 POWER SUPPLY, RESET, AND CLOCKS
S1C17M20/M21/M22/M23/M24/M25
Seiko Epson Corporation
2-5
TECHNICAL MANUAL (Rev. 1.0)
CLG
IOSCCLK
SYSCLK
SLEEP, WAKE-UP
IOSCEN
CLKSRC[1:0]
CLKDIV[1:0]
WUPMD
CLKSRC[x:0]
CLKDIV[x:0]
WUPSRC[1:0]
WUPDIV[1:0]
IOSC
oscillator
circuit
Divider
Clock
selector
System
clock
controller
OSC1CLK
OSC1EN
OSC1
oscillator
circuit
Divider
OSC3CLK
OSC3EN
OSC3
oscillator
circuit
Divider
EXOSCCLK
EXOSCEN
EXOSC
clock input
circuit
FOUT
output
circuit
Clock
selector
Peripheral circuit 1
CLKSRC[x:0]
CLKDIV[x:0]
Clock
selector
Peripheral circuit n
To CPU and bus
Inter
nal data
bu
s
OSC1
( )
( )
OSC2
EXOSC
OSC3
OSC4
X’tal3/Ceramic3
X’tal1
FOUT
FOUTDIV[2:0]
FOUTEN
Figure 2.3.1.1 CLG Configuration
2.3.2 Input/Output Pins
Table 2.3.2.1 lists the CLG pins.
Table 2.3.2.1 List of CLG Pins
Pin name
I/O
*
Initial status
*
Function
OSC1
A
–
OSC1 oscillator circuit input
OSC2
A
–
OSC1 oscillator circuit output
OSC3
A
–
OSC3 oscillator circuit input
OSC4
A
–
OSC3 oscillator circuit output
EXOSC
I
I
EXOSC clock input
FOUT
O
O (L)
FOUT clock output
*
Indicates the status when the pin is configured for CLG.
If the port is shared with the CLG input/output function and other functions, the CLG function must be assigned to
the port. For more information, refer to the “I/O Ports” chapter.
2.3.3 Clock Sources
IOSC oscillator circuit
The IOSC oscillator circuit features a fast startup and no external parts are required for oscillating. Figure 2.3.3.1
shows the configuration of the IOSC oscillator circuit.