SIC63616-(Rev. 1.0) NO. P40
3240-0412
4.4.3 OSC1 oscillation circuit
The OSC1 oscillation circuit generates the 32.768 kHz (Typ.) system clock which is used during low speed
(low power) operation of the CPU and peripheral circuits. Furthermore, even when OSC3 is used as the
system clock, OSC1 continues to generate the source clock for the clock timer and stopwatch timer. This
oscillation circuit stops when the SLP instruction is executed.
Figure 4.4.3.1 shows the configuration of the OSC1 oscillation circuit.
f
OSC1
V
SS
V
SS
OSC2
OSC1
X'tal
C
G1
SLEEP status
Fig. 4.4.3.1 OSC1 oscillation circuit (crystal oscillation)
A crystal oscillation circuit can be configured simply by connecting a crystal oscillator X'tal (Typ. 32.768
kHz) between the OSC1 and OSC2 terminals along with a trimmer capacitor C
G1
(0–25 pF) between the
OSC1 terminal and V
SS
.
4.4.4 OSC3 oscillation circuit
The OSC3 oscillation circuit generates the system clock to run the CPU and some peripheral circuits at high
speed. This oscillation circuit stops when the SLP instruction is executed or the OSCC register is set to "0".
The oscillator type can be selected from ceramic or CR by mask option.
Figure 4.4.4.1 shows the configuration of the OSC3 oscillation circuit.
f
OSC3
Oscillation circuit
control signal
SLEEP status
V
SS
OSC4
OSC3
C
D3
C
G3
R
f
Ceramic
(1) Ceramic oscillation circuit
f
OSC3
Oscillation circuit
control signal
SLEEP status
OSC4
OSC3
R
CR
(2) CR oscillation circuit
Fig. 4.4.4.1 OSC3 oscillation circuit
When ceramic oscillation circuit (Max. 4.2 MHz) is selected, connect a ceramic oscillator (Ceramic) between
the OSC3 and OSC4 terminals and connecting two capacitors (C
G3
, C
D3
) between the OSC3 terminal and
V
SS
, and between the OSC4 terminal and V
SS
, respectively.
When CR oscillation (Max. 2 MHz) is selected, connect a resistor (R
CR
) between the OSC3 and OSC4 termi-
nals.