
24
EPSON
S1C63466 TECHNICAL MANUAL
CHAPTER 4: PERIPHERAL CIRCUITS AND OPERATION (Oscillation Circuit)
VSS
CGX
X'tal
OSC2
OSC1
R
DX
C DX
To CPU
(and peripheral circuits)
FX
VSS
OSC2
OSC1
C CR
To CPU
(and peripheral circuits)
R
CR1
(b) CR oscillation circuit
Fig. 4.3.2.1 OSC1 oscillation circuit
(a) Crystal oscillation circuit
4.3 Oscillation Circuit
4.3.1 Configuration of oscillation circuit
The S1C63466 has two oscillation circuits (OSC1 and OSC3). OSC1 is either a crystal or a CR oscillation
circuit that supplies the operating clock to the CPU and peripheral circuits. OSC3 is either a CR or a
ceramic oscillation circuit. When processing with the S1C63466 requires high-speed operation, the CPU
operating clock can be switched from OSC1 to OSC3 by the software. To stabilize operation of the internal
circuits, the operating voltage VD1 must be switched according to the oscillation circuit to be used. Figure
4.3.1.1 is the block diagram of this oscillation system.
Oscillation circuit control signal
CPU clock selection signal
To CPU
To peripheral circuits
Clock
switch
Oscillation system
voltage regulator
OSC3
oscillation circuit
OSC1
oscillation circuit
Operating voltage selection signal
VD1
Divider
Fig. 4.3.1.1 Oscillation system block diagram
4.3.2 OSC1 oscillation circuit
The OSC1 oscillation circuit generates the main clock for the CPU and the peripheral circuits. Either the
crystal oscillation circuit or the CR oscillation circuit can be selected as the circuit type by mask option.
The oscillation frequency of the crystal oscillation circuit is 32.768 kHz (Typ.) and the CR oscillation
circuit is 60 kHz (Typ.).
Figure 4.3.2.1 is the block diagram of the OSC1 oscillation circuit.