Osc1 Oscillation Circuit - Epson S1C63666 Technical Manual

CHAPTER 4: PERIPHERAL CIRCUITS AND OPERATION (Oscillation Circuit)
4.4 Oscillation Circuit
4.4.1 Configuration of oscillation circuit
The S1C63666 has two oscillation circuits (OSC1 and OSC3). OSC1 is a crystal oscillation circuit that
supplies the operating clock to the CPU and peripheral circuits. OSC3 is either a CR or a ceramic oscilla-
tion circuit. When processing with the S1C63666 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 must be switched according to the oscillation circuit to be used. Figure 4.4.1.1 is the
block diagram of this oscillation system.
Voltage regulator for

OSC1 oscillation circuit

High-speed operation
voltage regulator
4.4.2 OSC1 oscillation circuit
The OSC1 crystal oscillation circuit generates the main clock for the CPU and the peripheral circuits. The
oscillation frequency is 32.768 kHz (Typ.).
Figure 4.4.2.1 is the block diagram of the OSC1 oscillation circuit.
As shown in Figure 4.4.2.1, the crystal oscillation circuit can be configured simply by connecting the
crystal oscillator (X'tal) of 32.768 kHz (Typ.) between the OSC1 and OSC2 terminals and the trimmer
capacitor (C ) between the OSC1 and V
GX
32
OSC1
oscillation circuit
V
OSC
OSC3
oscillation circuit
V
D1
Fig. 4.4.1.1 Oscillation system block diagram
C
GX
OSC1
OSC2
V
SS
Fig. 4.4.2.1 OSC1 oscillation circuit
terminals.
SS
Divider
Clock
switch
CPU clock selection signal
Oscillation circuit control signal
Operating voltage selection signal
To CPU
(and peripheral circuits)
C
DX
V
SS
EPSON
To peripheral circuits
To CPU
S1C63666 TECHNICAL MANUAL