SAF-C502-2R20N Siemens Semiconductor Group, SAF-C502-2R20N Datasheet - Page 30

• Manufacturer Part Number: SAF-C502-2R20N
• Description: 8-Bit CMOS Microcontroller
• Manufacturer: Siemens Semiconductor Group

2) Oscillator Watchdog (OWD)
The OWD consists of an internal RC oscillator which provides the reference frequency for the
comparison with the frequency of the on-chip oscillator.
Figure 6 shows the block diagram of the oscillator watchdog unit while table 14 shows the effect
when the OWD becomes activ/inactiv.
Note: The OWD is always enabled!
Figure 6
Functional Block Diagram of the Oscillator Watchdog
Table 14
Effects of the OWD
Semiconductor Group
Conditions
f
f
OSC
OSC
<
>
f
f
RC
RC
/5
/5
Effect
Switch input of internal clock system to RC oscillator output
Activating internal reset at the same time (reset sequence is clocked by
RC-oscillator).
Exception from effects of a Hardware Reset:
Watchdog Timer Status Flag, WDTS is not reset
Oscillator Watchdog Status Flag, OWDS is set
Input of internal clock system is
When failure condition (
final reset phase of typ. 1 ms in order to allow the external oscillator to
stabilize.
f
OSC
29
<
f
RC
f
/5) disappears the part executes a
OSC
/2.
C502