ST6208C/ST6209C/ST6210C/ST6220C
CLOCK SYSTEM (Cont’d)
5.1.1 Main Oscillator
Table 6. Oscillator Configurations
Hardware Configuration
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).
External Clock
ST6
OSCin
OSCout
NC
EXTERNAL
CLOCK
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).
2)
Crystal/Resonator Clock
ST6
OSCin
OSCout
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
C
C
L2
L1
software instruction at a clock frequency f
.
LOAD
CAPACITORS
LFAO
3)
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).
RC Network
ST6
OSCin
NC
OSCout
R
NET
LFAO
ST6
OSCin
OSCout
NC
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.
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STMICROELECTRONICS [ ST ]
