How detect the PLC in stop mode

[jcp]

Hi;
How can i detect that PLC in stop mode. Becuase there are some options which can be happen:
1. If operator stop the PLC by pressing ALT--R then on the HMI i want to detect the plc in stop mode and run the xyz logic.
2. May be from the key on CPU?
regards;
I stop the plc from software OK and PWR light solid green but RUN light off. I do not know how can i detect?
Second i read SVC_REQ but it tells me which i understand
two states 1. RUN/ENABLE I/O 2. RUN/DISABLE I/O
Plz help me
Regards

 

[I is a noob]

Set up a heart beat if you can alarm off of unchaging data maybe? Try the always on %S( 7 or 8, i can never remember) and have it going to an M-Coil that you will not use for any thing other than this. Trigger alarm on a 0/Off status of the internal bit. The second option will only work if you put it in to Stop/IO Disabled or it it Fault Stops on its own. The heart beat option work regardless but you will have to set up some type of refrence to time to determine if it has stopped proccessing data.

 

[Steve Bailey]

In ladder logic use a -] [- contact addressed to %S0001 to set a %M bit. Use a -]/[- contact addressed to %S0002 to reset the same %M bit. When the %M bit is on, the program is running. If it is off, the program is stopped.

1. If operator stop the PLC by pressing ALT--R then on the HMI i want to detect the plc in stop mode and run the xyz logic.

What device is going to run the "xyz logic"?

Second i read SVC_REQ but it tells me which i understand
two states 1. RUN/ENABLE I/O 2. RUN/DISABLE I/O

If the PLC isn't running, how do expect it to execute a SVC_REQ finction?

 

[caddymac]

Set up a heart beat if you can alarm off of unchaging data maybe? Try the always on %S( 7 or 8, i can never remember)

%S0007 is the always on bit. I remember this by thinking the following - James Bond (007) movies are ALWAYS ON television.

 

[I is a noob]

Thanks for that, had to re-re-read that last post....

 

[I is a noob]

In ladder logic use a -] [- contact addressed to %S0001 to set a %M bit. Use a -]/[- contact addressed to %S0002 to reset the same %M bit.

Using set and reset coils? Wonder why they didn't put in a %S that would read run or stop in this fashion....

 

[RussB]

You could also use the just "Last Scan" bit (%S2) to turn on or off an internal to monitor. Similar to what Steve is suggesting.