ICP DAS USA I-7521, User Manual

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I-7521/I-7522/I-7522A/I-7523/I-7524/I-7527 User’s Manual,Ver2.5 Aug.2015
66
4.5
Module WatchDog Application Notes
The “$AA5” command is designed to detect any module hardware
watchdog failure. If the module was malfunctioned, the module
hardware watchdog circuit will reset the module. After reset, the output
state of the module will revert to its initial start values. The start value
may be different from the output values prior to the module reset.
Therefore the user must send the output commands to the module
again in order to maintain the same output state both before and after
the module watchdog reset.
The flow chart for module hardware watchdog failure detection is as
follows:
Send “$AA5” and determine
S=1
Function 1
Function n
Send “$AA5” and determine
S=?
S=0
S=1
All DO will now be in their
start-value.
Send a “$AAZNV” command
to reset the DO modules to
their desire states.