ST62T25CM6/TR STMicroelectronics, ST62T25CM6/TR Datasheet - Page 21

• Manufacturer Part Number: ST62T25CM6/TR
• Description: IC MCU 8BIT W/ADC 28-SOIC
• Manufacturer: STMicroelectronics
• Series: ST6r

Specifications of ST62T25CM6/TR

• Core Processor: ST6
• Core Size: 8-Bit
• Speed: 8MHz
• Peripherals: LVD, POR, WDT
• Number Of I /o: 20
• Program Memory Size: 4KB (4K x 8)
• Program Memory Type: OTP
• Ram Size: 64 x 8
• Voltage - Supply (vcc/vdd): 3 V ~ 6 V
• Data Converters: A/D 16x8b
• Oscillator Type: Internal
• Operating Temperature: -40°C ~ 85°C
• Package / Case: 28-SOIC (7.5mm Width)
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Eeprom Size: -
• Connectivity: -

CLOCK SYSTEM (Cont’d)
5.1.2 Oscillator Safeguard (OSG)
The Oscillator Safeguard (OSG) feature is a
means of dramatically improving the operational
integrity of the MCU. It is available when the OSG
ENABLED option is selected in the option byte (re-
fer to the Option Bytes section of this document).
The OSG acts as a filter whose cross-over fre-
quency is device dependent and provides three
basic functions:
– Filtering spikes on the oscillator lines which
– Management of the Low Frequency Auxiliary
– Automatically limiting the f
5.1.2.1 Spike Filtering
Spikes on the oscillator lines result in an effectively
increased internal clock frequency. In the absence
of an OSG circuit, this may lead to an over fre-
quency for a given power supply voltage. The
OSG filters out such spikes (as illustrated in
10). In all cases, when the OSG is active, the max-
Figure 10. OSG Filtering Function
Figure 11. LFAO Oscillator Function
would result in driving the CPU at excessive fre-
quencies
Oscillator (LFAO), (useable as low cost internal
clock source, backup clock in case of main oscil-
lator failure or for low power consumption)
a function of supply voltage, to ensure correct
operation even if the power supply drops.
f
f
f
OSC
LFAO
INT
f
f
f
OSC
OSG
INT
MAIN OSCILLATOR
STOPS
INT
clock frequency as
f
OSC>
f
OSG
INTERNAL CLOCK DRIVEN BY LFAO
Figure
imum internal clock frequency, f
f
5.1.2.2
Variations
Over-frequency, at a given power supply level, is
seen by the OSG as spikes; it therefore filters out
some cycles in order that the internal clock fre-
quency of the device is kept within the range the
particular device can stand (depending on V
and below f
cy with OSG enabled.
5.1.2.3 LFAO Management
When the OSG is enabled, the Low Frequency
Auxiliary Oscillator can be used (see
5.1.3).
Note: The OSG should be used wherever possible
as it provides maximum security for the applica-
tion. It should be noted however, that it can in-
crease power consumption and reduce the maxi-
mum operating frequency to f
Characteristics section).
Caution: Care has to be taken when using the
OSG, as the internal frequency is defined between
a minimum and a maximum value and may vary
depending on both V
cise timing measurements, it is not recommended
to use the OSG.
OSG
, which is supply voltage dependent.
RESTARTS
MAIN OSCILLATOR
Management
ST6215CM-Auto ST6225CM-Auto
OSG
: the maximum authorised frequen-
DD
f
OSC<
and temperature. For pre-
f
OSG
of
OSG
Supply
INT
(see Electrical
, is limited to
Voltage
Section
21/100
DD
),
1