Epson S1C17M01 Technical Manual page 25

OSC1
oscillator
circuit
The IOSC oscillator circuit output clock IOSCCLK is used as SYSCLK at booting. The IOSC oscillator circuit
is equipped with an auto-trimming function that automatically adjusts the frequency. This helps reduce fre-
quency deviation due to unevenness in manufacturing quality, temperature, and changes in voltage. For more
information on the auto-trimming function and the oscillation characteristics, refer to "IOSC oscillation auto-
trimming function" in this chapter and "IOSC oscillator circuit characteristics" in the "Electrical Characteris-
tics" chapter, respectively.
OSC1 oscillator circuit
The OSC1 oscillator circuit is a high-precision and low-power oscillator circuit that uses a 32.768 kHz crystal
resonator. Figure 2.3.3.2 shows the configuration of the OSC1 oscillator circuit.
OSC1 oscillator circuit
V
DD
External gate
Internal variable
capacitor C
G1
OSC1
gate capacitor C
V
X'tal1 SS
V
DD
OSC2
External drain
V
SS
capacitor C
D1
Internal drain capacitor C
This oscillator circuit includes a gain-controlled oscillation inverter and a variable gate capacitor allowing use
of various crystal resonators with ranges from cylinder type through surface-mount type.
The oscillator circuit also includes a feedback resistor and a drain resistor, so no external parts are required ex-
cept for a crystal resonator. The embedded oscillation stop detector, which detects oscillation stop and restarts
the oscillator, allows the system to operate in safety under adverse environments that may stop the oscillation.
The oscillation startup control circuit operates for a set period of time after the oscillation is enabled to assist
the oscillator in initiating, this makes it possible to use a low-power resonator that is difficult to start up. For the
recommended parts and the oscillation characteristics, refer to the "Basic External Connection Diagram" chap-
ter and "OSC1 oscillator circuit characteristics" in the "Electrical Characteristics" chapter, respectively.
Note: Depending on the circuit board or the crystal resonator type used, an external gate capacitor C
and a drain capacitor C
EXOSC clock input
EXOSC is an external clock input circuit that supports square wave and sine wave clocks. Figure 2.3.3.3 shows
the configuration of the EXOSC clock input circuit.
S1C17M01 TECHNICAL MANUAL
(Rev. 1.2)
IOSC oscillator circuit
IOSCEN
Clock
oscillator
Auto-
OSC1CLK
trimming
circuit
IOSCSTM
Figure 2.3.3.1 IOSC Oscillator Circuit Configuration
OSC1EN INV1N[1:0] INV1B[1:0]
Oscillation startup
control circuit
Gain-controlled
oscillation
inverter
GI1
CGI1[2:0]
Feedback Drain
resistor R resistor R
F1 D1
DI1
Figure 2.3.3.2 OSC1 Oscillator Circuit Configuration
may be required.
D1
Seiko Epson Corporation
2 POWER SUPPLY, RESET, AND CLOCKS
Oscillation
stabilization
waiting circuit
Interrupt
control circuit
IOSCSTAIF
IOSCSTAIE
Restart
Oscillation
signal
stop
detector OSC1WT[1:0]
Oscillation
Noise filter stabilization
waiting circuit
Interrupt
control circuit
OSC1STAIE
IOSCCLK
Interrupt
controller
OSC1CLK
Interrupt
controller
OSC1STAIF
G1
2-5