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UPGRADING FROM ST625X/6XB TO ST625X/6XC

Figure 1. Low Voltage Detector Reset

1.1.2 Oscillator Safeguard (OSG)

The Oscillator Safeguard (OSG) feature is a means of dramatically improving the operational

integrity of the MCU.The OSG function is enabled by setting the OSG option bit in the Option

Byte (refer to the Option Bytes section in the device data sheet).

The OSG acts as a filter whose cross-over frequency is device dependent and provides three

basic functions:

– Filtering spikes on the oscillator lines which would result in driving the CPU at excessive fre-

quencies

– Management of the Low Frequency Auxiliary Oscillator (LFAO), (useable as low cost internal

clock source, backup clock in case of main oscillator failure or for low power consumption)

rect operation even if the power supply drops.

The OSG function is illustrated in Figure 2. For more details on it, please refer to the Clock,

Supply and Reset section in the device data sheet.

Please note that the OSG should be used wherever possible as it provides maximum security

for the application. It should be noted however, that it can increase power consumption and re-

of the device data sheet).

Caution: Care has to be taken when using the OSG, as the internal frequency is defined be-

ture. For precise timing measurements, it is not recommended to use the OSG.

RESET