
S1C6F567 TECHNICAL MANUAL
EPSON
23
CHAPTER 4: PERIPHERAL CIRCUITS AND OPERATION (Oscillation Circuit)
4.3 Oscillation Circuit
4.3.1 Configuration of oscillation circuit
The S1C6F567 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 a ceramic oscillation circuit.
When processing with the S1C6F567 requires high-speed operation, the CPU operating clock can be
switched from OSC1 to OSC3 by software. 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
OSC3
oscillation circuit
OSC1
oscillation circuit
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. The oscilla-
tor type is a crystal oscillation circuit and the oscillation frequency is 32.768 kHz (Typ.).
Figure 4.3.2.1 is the block diagram of the OSC1 oscillation circuit.
VSS
CGX
X'tal
OSC2
OSC1
R
DX
C DX
To CPU
(and peripheral circuits)
FX
VSS
Fig. 4.3.2.1 OSC1 oscillation circuit
As shown in Figure 4.3.2.1, 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 (CGX) between the OSC1 and VSS terminals.
4.3.3 OSC3 oscillation circuit
The S1C6F567 has built-in the OSC3 oscillation circuit that generates the CPU's sub-clock (Max. 3.58
MHz) for high speed operation and the source clock for peripheral circuits needing a high speed clock
(programmable timer, FOUT output). The oscillator type is a ceramic oscillation circuit and a ceramic
oscillator and two capacitors (gate and drain capacitance) are required.
Figure 4.3.3.1 is the block diagram of the OSC3 oscillation circuit.
VSS
CGC
CDC
Ceramic
OSC4
OSC3
R
RDC
FC
To CPU
(and some peripheral circuits)
Oscillation circuit control signal
Fig. 4.3.3.1 OSC3 oscillation circuit