Epson S1C17W03 Technical Manual page 30

2 POWER SUPPLY, RESET, AND CLOCKS
OSC1 oscillator circuit
OSC1EN
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
OSC3 oscillator circuit
The OSC3 oscillator circuit is a high-speed oscillator circuit that allows software to select the oscillator type
from three types shown below. Figure 2.3.3.3 shows the configuration of the OSC3 oscillator circuit.
Crystal/ceramic oscillator
This oscillator circuit includes a feedback resistor and a drain resistor, so no external part is required except
for a crystal/ceramic resonator. The embedded gain-controlled inverter allows selection of the resonator
from a wide frequency range.
CR oscillator
This oscillator circuit includes an oscillation capacitor (C
sistor (R ). No external part is required except for R
CR3
Internal oscillator
This oscillator circuit operates without any external parts, and its oscillation frequency can be selected via
software.
Notes: • The maximum value of the OSC3 oscillator circuit oscillation frequency f
supply voltage V
ating Conditions" in the "Electrical Characteristics" chapter.
• When the CR oscillator is selected, the changes in the signals output from the I/O pins adja-
cent to the OSC3 and OSC4 pins may affect the oscillation frequency.
• When the internal oscillator is selected, be sure to avoid using the pins to which OSC3 and
OSC4 are assigned as input pins, as it may affect the oscillation frequency.
2-8
OSC1BUP 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
OSC1 oscillator circuit
voltage regulator
Figure 2.3.3.2 OSC1 Oscillator Circuit Configuration
may be required.
D1
value. For the oscillation frequency range, refer to "Recommended Oper-
DD
Seiko Epson Corporation
OSDRB OSDEN
Restart
signal Oscillation
stop detector
OSC1WT[1:0]
Oscillation
Noise filter stabilization
waiting circuit
Interrupt control
OSC1STPIE
circuit
OSC1STAIE
), and the frequency can be adjusted by the re-
CR3
.
CR3
S1C17W03/W04 TECHNICAL MANUAL
OSC1CLK
OSC1STPIF
OSC1STAIF
Interrupt
controller
G1
depends on the
OSC3
(Rev. 1.2)