ST6215C_09 datasheet(20/105 Pages) STMICROELECTRONICS

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ST6215C ST6225C

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CLOCK SYSTEM (Cont’d)

5.1.1 Main Oscillator

The oscillator configuration is specified by select-

ing the appropriate option in the option bytes (refer

to the Option Bytes section of this document).

When the CRYSTAL/RESONATOR option is se-

lected, it must be used with a quartz crystal, a ce-

ramic resonator or an external signal provided on

the OSCin pin. When the RC NETWORK option is

selected, the system clock is generated by an ex-

ternal resistor (the capacitor is implemented inter-

nally).

The main oscillator can be turned off (when the

OSG ENABLED option is selected) by setting the

OSCOFF bit of the ADC Control Register (not

available on some devices). This will automatically

start the Low Frequency Auxiliary Oscillator

(LFAO).

The main oscillator can be turned off by resetting

the OSCOFF bit of the A/D Converter Control Reg-

ister or by resetting the MCU. When the main os-

cillator starts there is a delay made up of the oscil-

lator start-up delay period plus the duration of the

software instruction at a clock frequency fLFAO.

Caution: It should be noted that when the RC net-

work option is selected, the accuracy of the fre-

quency is about 20% so it may not be suitable for

some applications (For more details, please refer

to the Electrical Characteristics Section).

Table 5. Oscillator Configurations

Notes:

1. To select the options shown in column 1 of the above

table, refer to the Option Byte section.

2.This schematic are given for guidance only and are sub-

ject to the schematics given by the crystal or ceramic res-

onator manufacturer.

3. For more details, please refer to the Electrical Charac-

teristics Section.

Hardware Configuration

OSCin

OSCout

EXTERNAL

ST6

CLOCK

External Clock

OSCin

OSCout

LOAD

CAPACITORS 3)

ST6

CL2

CL1

Crystal/Resonator Clock 2)

OSCin

OSCout

ST6

RNET

RC Network

OSCin

OSCout

ST6

LFAO

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