
Preliminary Technical Data
AD5100
Rev. PrJ | Page 15 of 32
Watchdog Input
The Watch-Dog Input (WDI) circuit attempts to reset the
system to a known good state if a software or hardware glitch
renders the system processor inactive for a duration that is
longer than the timeout period. There is an 8-step
programmable timeout period from 100ms to 2000ms.The
watchdog circuit is independent of the CPU clock that the
watchdog is monitoring.
Watchdog is disabled during power-up. WDI starts
monitoring once the RESET is high. Unique to AD5100, it
provides a Standard or Advance Watchdog monitoring
function. In the defaulted Standard Watchdog mode, if WDI
remains either high or low for longer than the timeout
period, a reset pulse is generated in an attempt to allow the
system processor to re-establish the WDI signal. The reset
pulses continue indefinitely until a valid watchdog signal, a
rising or falling edge signal at the WDI, is received. The
internal watchdog timer clears whenever reset is asserted.
The Standard WDI and RESET timing diagrams are shown in
Figure 12.
RESET
WDI
t
WD
t
WDR
t
WDR
t
WD
Continuous pulses until WD awakes
reset pulse
t
WDI
Figure 12. Standard Watchdog – Pulsing Reset Until Watchdog Awakes.
On the other hand, the AD5100 can be programmed to an
Advance Watchdog mode such that when the watchdog
remains inactive longer than three times the watchdog
timeout period, at the forth time the
SHDN and RESET
will be
asserted and released after 1 second. These actions repeat
indefinitely, unless it is interferred by the user, if the
processor is not responding. The Advance WDI and RESET
timing diagrams are shown in Figure 13.
RESET
SHDN
WDI
t
WD_SHDN
t
WD
t
WDR
t
WDR
t
WD
3 reset pulses
1 reset pulse
Shutdown at 4th reset pulse
Release after 1s
t
WDI
Figure 13. Advance Watchdog –
SHDN
Asserted After Three Trials of Reseting the Watchdog.
SHDN
Released After 1 second and the cycle repeats.
The range of Watchdog Timeout is shown in Table 6a and
the programming code of the selected-timeout is found in
Table 6b. The default timeout is 1500ms.
If WDI is floating, the watchdog is disabled by default.
However, floating watchdog can be enabled through I2C