C164CI_02 Datasheet, PDF (36/484 Pages) Infineon Technologies AG – 16-Bit Single-Chip Microcontroller

C164CI/C164SI
Derivatives
Architectural Overview
Watchdog Timer
The Watchdog Timer is one of the fail-safe mechanisms implemented in the C164CI to
prevent the controller from malfunctioning for longer periods of time.
The Watchdog Timer is always enabled after a reset of the chip, and can be disabled
only for the time interval before the EINIT (end of initialization) instruction has been
executed. Thus, the chip’s start-up procedure is always monitored. The software must
be designed to service the Watchdog Timer before it overflows. If the software fails to do
so, due to either hardware or software related failures, the Watchdog Timer overflows
and generates an internal hardware reset and pulls the RSTOUT pin low to allow
external hardware components to reset.
The Watchdog Timer is a 16-bit timer, clocked with the CPU clock divided by 2, 4, 128, or
256. The high byte of the Watchdog Timer register can be set to a prespecified reload
value (stored in WDTREL) to allow further variation of the monitored time interval. Each
time it is serviced by the application software, the high byte of the Watchdog Timer is
reloaded. Thus, time intervals between 21 µs and 671 ms can be monitored (@ 25 MHz).
The default Watchdog Timer interval after reset is 5.2 ms (@ 25 MHz).
2.4
Power Management Features
The basic power reduction modes (Idle and Power Down) are enhanced by additional
power management features (see below). These features can be combined to reduce
the controller’s power consumption to correspond to the application’s possible minimum.
• Flexible clock generation
• Flexible peripheral management (peripherals can be dis/enabled separately or in
groups)
• Periodic wakeup from Idle mode via RTC timer
The listed features provide effective means to realize standby conditions for the system
with an optimum balance between power reduction (standby time) and peripheral
operation (system functionality).
User’s Manual
2-18
V3.1, 2002-02