ICP DAS USA ET-7000 series, Руководство пользователя

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Appendix D: Modbus Application Notes
ET-7000 AIO User Manual, Apr. 2009, V1.04, EMH-011-104
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136
Appendix D: Modbus Application Notes
Dual Watchdog
Dual Watchdog consists of
Module Watchdog
and
Host Watchdog
.
The
Module Watchdog
is a built-in hardware circuit that will reset the CPU module if a failure
occurs in either the hardware or the software. If the application does not refresh the watchdog
timer within 0.8 seconds, the watchdog circuit will initiate a reset of the CPU.
The
Host Watchdog
is a software function that can be used to monitor the operating status
of the host. Its purpose is to prevent network communication problems or a host failure. If the
Watchdog timeout interval expires, the module will return all outputs to a predefined Safe
value (Refer to the
Safe Value
application note), which can prevent the controlled target from
unexpected situation.