Atmel ATA6264 - Manual (Page 48)

48
4929B–AUTO–01/07
ATA6264 [Preliminary]
Requirements for successful trigger:
• Minimum one valid different serial interface command between two trigger watchdog
commands is necessary. Exception: First trigger watchdog command need not be preceded
by a different serial interface command.
• Cyclic repetition for the trigger watchdog command within ±25% tolerance is necessary.
Incorrect trigger causes RESQ active.
The prescaler will be set to its default value with RESQ = low
Initial phase:
Timing for the first trigger watchdog is fixed to 16 ms after RESQ changes from low to high (trig-
ger window ±25% means ±4-ms trigger window for first trigger watchdog command). After the
first watchdog trigger, the prescaler can be reconfigured within a specified time window (< 1 ms).
Only one configuration command is allowed in this time window. For watchdog trigger handling,
the Serial Interface Reconfigure command can be chosen as a different serial interface com-
mand. Any further configuration inside or outside this time window will cause an immediate reset
via RESQ.
Figure 16-2. Reconfiguration Prescaler Functional Principle
Serial
interface
communication
chip
internal
trigger
window
No succesful
reconfiguration
Succesful
reconfiguration
1 ms 1 ms
RESQ
t
t
t
active
inactive
re-configure
prescaler
re-configure
prescaler
T
rg Wdg
CMD
T
rg Wdg
CMD