Programmable Serial-to-Ethernet Device Server
PDS Series User Manual, Version 2.5, Mar. 2019
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Application Notes
Hot Watchdog Status
The Power On Reset or Module Watchdog Reset will return all output settings to Power On Values.
The Host Watchdog Timeout will return all output values to Safe Values. Additionally, the status of
the Host Watchdog, which can be read using the ~AA0 command, will be recorded as 04, and
output commands will be ignored until the status is cleared to 0 by using command ~AA1.
Dual Watchdog Operation
Dual Watchdog = Module Wa Host Watchdog
The Module Watchdog is a hardware reset circuit that is used to monitor the operating status of
the module. When working in harsh or noisy environments, the module may be interrupted by
external signals. The circuit can let the module reboot automatically and to work continues without
halt.
The Host Watchdog is a software function that is used to monitor the operating status of the host.
Its purpose is to keep PDS’s output in a safe state when there is network communication problem
or host PC halt. If the timeout interval expires, the module will turn all outputs to the predefined
Safe Value and prevent unexpected situation from occurring.
The PDS series with Dual Watchdog will make the control system more reliable and stable.
Reset Status
The Reset Status is set when the module is powered on or if it is reset by the Module Watchdog.
The status can be cleared by using the Reset Status ($AA5) command. This is useful for checking the
operating status of the module. When the Reset Status is set it means that the module has been
reset and the output can be changed to the Power On Value. When the Reset Status is clear it
means the module was not been reset, and the output was not changed.
