Osc3 Oscillation Circuit - Epson S1C63666 Technical Manual

4.4.3 OSC3 oscillation circuit

The S1C63666 has built-in the OSC3 oscillation circuit that generates the CPU's sub-clock (Max. 4 MHz)
for high speed operation and the source clock for peripheral circuits needing a high speed clock (pro-
grammable timer, FOUT output). The mask option enables selection of the oscillator type from CR
(external R type), CR (built-in R type) and ceramic oscillation circuit. When CR oscillation (external R
type) is selected, only a resistance is required as an external element. When ceramic oscillation is selected,
a ceramic oscillator and two capacitors (gate and drain capacitance) are required. When CR oscillation
(built-in R type) is selected, no external element is required.
Figure 4.4.3.1 is the block diagram of the OSC3 oscillation circuit.
C
C
V
SS
As shown in Figure 4.4.3.1, the CR oscillation circuit (external R type) can be configured simply by
connecting the resistor R
Chapter 7, "Electrical Characteristics" for resistance value of R
When ceramic oscillation is selected, the ceramic oscillation circuit can be configured by connecting the
ceramic oscillator (Max. 4 MHz) between the OSC3 and OSC4 terminals, capacitor C
and OSC4 terminals, and capacitor C
connect capacitors that are about 30 pF. To reduce current consumption of the OSC3 oscillation circuit,
oscillation can be stopped by the software (OSCC register).
S1C63666 TECHNICAL MANUAL
CHAPTER 4: PERIPHERAL CIRCUITS AND OPERATION (Oscillation Circuit)
C
CR
OSC3
OSC4
(a) CR oscillation circuit (external R type)
C
CR
(b) CR oscillation circuit (built-in R type)
GC
OSC3
DC
OSC4
(c) Ceramic oscillation circuit
Fig. 4.4.3.1 OSC3 oscillation circuit
between the OSC3 and OSC4 terminals when CR oscillation is selected. See
CR
between the OSC4 and V
DC
Table 4.4.3.1 OSC3 oscillation frequency
Oscillation circuit
Ceramic oscillation
CR oscillation (built-in R type)
CR oscillation (external R type)
To CPU
(and some peripheral circuits)
Oscillation circuit control signal
To CPU
(and some peripheral circuits)
Oscillation circuit control signal
To CPU
(and some peripheral circuits)
Oscillation circuit control signal
R
DC
.
CR
terminals. For both C
SS
Oscillation frequency
Max. 4 MHz
Typ. 1.1 MHz ±30%
200 kHz to 2 MHz
EPSON
between the OSC3
GC
and C ,
GC DC
33