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Is the connection hardwired, or over a network like DeviceNet or EtherNet/IP ?
Usually the Stop Asserted message means exactly what it says: something is holding a STOP signal true.
One common one is the digital inputs: DI1 is by default a STOP signal that has to be wired True to remove the STOP command.
That's inverse from the STOP bits in a network command. DI1=TRUE means "do not stop", while Bit 0 of the command word = TRUE means "stop".
There's a parameter that tells you which DPI adapter (onboard inputs, network, etc) is issuing the stop command; I know it's called "Stop Owner" but I don't have a PF70 manual at my fingertips to tell you which parameter number it is. I think there's an "owners" section of the parameter list to tell you which part of the drive's control structure is issuing starts and stops and reference commands.