Operations - Epson S1C17M12 Technical Manual

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 2.3.3.2 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.
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.
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
For the recommended parts and the oscillation characteristics, refer to the "Basic External Connection Dia-
gram" chapter and "OSC3 oscillator circuit characteristics" in the "Electrical Characteristics" chapter, respec-
tively.
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.
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.

2.3.4 Operations

Oscillation start time and oscillation stabilization waiting time
The oscillation start time refers to the time after the oscillator circuit is enabled until the oscillation signal is ac-
tually sent to the internal circuits. The oscillation stabilization waiting time refers to the time it takes the clock
to stabilize after the oscillation starts.
2-6
OSC3 oscillator circuit
OSC3MD[1:0]
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
Figure 2.3.3.2 OSC3 Oscillator Circuit Configuration
EXOSC clock
EXOSC
Figure 2.3.3.3 EXOSC Clock Input Circuit
Seiko Epson Corporation
Noise
filter
OSC3STAIE
Clock
input circuit
EXOSCEN
Input control
EXOSCCLK
circuit
OSC3WT[2:0]
Oscillation
stabilization OSC3CLK
waiting circuit
Interrupt
OSC3STAIF
control
circuit
S1C17M12/M13 TECHNICAL MANUAL
Interrupt
controller
(Rev. 1.2)