SAF-C517A Infineon Technologies AG, SAF-C517A Datasheet - Page 51

• Manufacturer Part Number: SAF-C517A
• Description: 8-bit CMOS MICROCONTROLLER
• Manufacturer: Infineon Technologies AG

Oscillator Watchdog
The oscillator watchdog unit serves for four functions:
Figure 25
Block Diagram of the Oscillator Watchdog
Semiconductor Group
XTAL2
XTAL1
– Monitoring of the on-chip oscillator’s function
– Fast internal reset after power-on
– Restart from the hardware power down mode.
The watchdog supervises the on-chip oscillator's frequency; if it is lower than the frequency of
the auxiliary RC oscillator in the watchdog unit, the internal clock is supplied by the RC
oscillator and the device is brought into reset; if the failure condition disappears (i.e. the on-
chip oscillator has a higher frequency than the RC oscillator), the part executes a final reset
phase of typ. 1 ms in order to allow the oscillator to stabilize; then the oscillator watchdog reset
is released and the part starts program execution again.
The oscillator watchdog unit provides a clock supply for the reset before the on-chip oscillator
has started. The oscillator watchdog unit also works identically to the monitoring function.
If the hardware power down mode is terminated the oscillator watchdog has to control the
correct start-up of the on-chip oscillator and to restart the program. The oscillator watchdog
function is only part of the complete hardware power down sequence; however, the watchdog
works identically to the monitoring function.
Oscillator
Oscillator
On-Chip
RC
f
3MHz
RC
÷ 5
÷ 2
f
f
1
2
OWDS
Comparator
Frequency
49
f
2
<
f
1
Delay
IP0 (A9 )
<
_
1
H
Internal Reset
Internal Clock
MCB03337
C517A