SLC 505 Hang


Thread Starter


Dear all,

I hv few cases of SLC 505 hang by itself without triggering any alarms at the system and at the SCADA (RS View) syst, & operator was not aware of it until is too late.

How to detect SLC 505 hang (Fault Led on, CPU Run Led Off) during operation at the SCADA (RS View)? Can SCADA detect and display the error code in the PLC CPU when the respective PLC hang?

Appreciate your advice.
Thank u

Tull, Leith \(Rockwell at Alcoa\)

Ths SLC-5/05 processor status table can still be read via message instructions in event of the processor faulting, but only under certain conditions. These include minor faults - software fault or I/O config fault, etc.. but cant be a communications port fault (will cause comms ports to fail). The PLC can not be communicated with however in the event of a major fault (in most cases anyway). This is what is happening I think to your SLC-5/05 as you said the Fault LED was ON, not blinking. A blinking Fault LED indicates a minor fault (recoverable) and the Fault LED always ON indicates a Major Fault (unrecoverable) Another way to help try to indicate a Fault with the processor is to hard wire a single output to something (Light or another interface) and use an unconditional rung in the ladder logic to energise it. Therefore whenever the SLC is actuively in run mode and scanning the Output will remain on, as soon as it is put into Program mode or Faults the output will turn OFF. Regards

Leith Tull

GMS Field Service Engineer
Rockwell Automation Australia Ltd. (Perth, WA)

Engelbert Rodríguez

Hi Lin, all the fault conditions and errors are registered in the status file (S File). You´re able to read any register on the status file with your SCADA software, you have to read the corresponding S file (see Help) in the same way you read inputs and outputs files from the PLC.

Good luck,

Engelbert Rodríguez

John van Dijk

I usually build in a 'heartbeat' signal; a time triggered bit send from PLC to SCADA and visa versa.
If this signal has not changed within a certain amount of time, the communication is dead, and an alarm can be generated.

Kind regards,
John van Dijk (Netherlands)

Yosef Feigenbaum

Hi Lim

1st of all you should find out why the 5/05 is "hanging".

As long as the fault LED on the 5/05 is not solid red and as long as the communications configuration has not been disrupted (ie. port failure) you will be able to read from the controllers data table including the status area.

Good luck,

(8{)} ( .)
[email protected]

try to use the status file of the processor
the file is acessed by the guide Processor Status/erros on the RSLOGIX 500 program


Jaison Carvalho
icq 63930339
msn [email protected]

Steve Myres, PE

The SLC will still communicate, even when faulted, so you may want to display some of the status bits in your MMI. You may want to look at some of the bits in S2:1 or other status registers.

Gerald Beaudoin

I had a similar problem with a 5/04. I found a tech bulletin on the Rockwell site... I think it was listed under "Comm failure" (don't have the # on hand but if you contact me off list I can dig it out). My problem would occur only during a download of the program to the PLC... a rather large program which would then hang the comm port of the PLC. The bulletin suggested that the problem was a timeout due to long network response time, perhaps due to heavy traffic. They suggested adding an SVC instruction part way through the program in order to make sure that the channel got serviced in time in spite of a long program scan times.

Good Luck

Gerald Beaudoin
[email protected]