Epson Arm S1C31 Series Technical Manual page 33

2 POWER SUPPLY, RESET, AND CLOCKS
OSC3 oscillator circuit
The OSC3 oscillator circuit is a high-speed oscillator circuit that allows software to select the oscillator type
from two different types shown below. Figure 2.3.3.3 shows the configuration of the OSC3 oscillator circuit.
Internal gate
capacitor C
External gate
GI3C
capacitor C
OSC3
G3
Peripheral
I/O
X'tal3/
I/O
port
Ceramic3
function 4
OSC4
External drain
Internal drain
capacitor C
D3
capacitor C
DI3C
OSC1
OSC1CLK
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.
Internal oscillator
This oscillator circuit features a fast startup and no external parts are required for oscillating. The
OSC3CLK frequency can be selected using the CLGOSC3.OSC3FQ[1:0] bits. This oscillator circuit
is equipped with an auto-trimming function that automatically adjusts the frequency. This helps reduce
frequency deviation due to unevenness in manufacturing quality, temperature, and changes in voltage. For
more information on the auto-trimming function, refer to "OSC3 oscillation auto-trimming function" in this
chapter.
For the recommended parts and the oscillation characteristics, refer to the "Basic External Connection Diagram"
chapter and "OSC3 oscillator circuit characteristics" in the "Electrical Characteristics" chapter, respectively.
EXOSC clock input
EXOSC is an external clock input circuit that supports square wave and sine wave clocks. Figure 2.3.3.4 shows
the configuration of the EXOSC clock input circuit.
EXOSC has no oscillation stabilization waiting circuit included, therefore, it must be enabled when a stabilized
clock is being supplied. For the input clock characteristics, refer to "EXOSC external clock input characteris-
tics" in the "Electrical Characteristics" chapter.
2-8
OSC3 oscillator circuit
OSC3MD
Selector
OSC3EN
Crystal/ceramic oscillator
OSC3INV[1:0]
Gain-
controlled
inverter
V
SS
Feedback Drain resistor
resistor R R
F3 D3
V
SS
Internal oscillator
OSC3FQ[1:0]
oscillator
trimming
OSC3SAJ[8:0]
OSC3STM
Figure 2.3.3.3 OSC3 Oscillator Circuit Configuration
EXOSC
Figure 2.3.3.4 EXOSC Clock Input Circuit
Seiko Epson Corporation
Noise filter
OSC3NF_N
OSC3STAIE
OSC3TEDIE
Clock
Auto-
circuit
EXOSC clock
input circuit
EXOSCEN
Input control
EXOSCCLK
circuit
OSC3WT[2:0]
Oscillation
stabilization
OSC3CLK
waiting circuit
Interrupt OSC3STAIF
control OSC3TEDIF
circuit
S1C31D41 TECHNICAL MANUAL
(Rev. 1.1)
CPU