CHAPTER 4: PERIPHERAL CIRCUITS AND OPERATION (Oscillation Circuit)

4.3 Oscillation Circuit

4.3.1 Configuration of oscillation circuit

The S1C63558 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 S1C63558 requires high-speed operation, the CPU operating clock can be switched from OSC1 to OSC3 by the software. Figure 4.3.1.1 is the block diagram of this oscillation system.

OSC1

Divider

oscillation circuit

To peripheral circuits

 

 

 

 

 

 

 

 

 

OSC3

 

 

 

Clock

 

To CPU

 

 

 

 

 

 

 

 

 

switch

 

 

oscillation circuit

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

CPU clock selection signal

Oscillation circuit control signal

VD1 Oscillation system voltage regulator

Fig. 4.3.1.1 Oscillation system block diagram

4.3.2 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 4.3.2.1 is the block diagram of the OSC1 oscillation circuit.

CGX

 

OSC1

To CPU

 

 

X'tal

 

(and peripheral circuits)

RFX

RDX

 

OSC2

C DX

 

 

VSS

 

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.

S1C63558 TECHNICAL MANUAL

EPSON

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