Profinet communication and PLC in STOP mode

Hi all,

I have made a S7 communication (TiaPortal v13) using PUT / GET functions between two S7-1500 PLCs. PLC1 (master) is doing the communication part (one-way).

The problem is that PUT / GET functions On PLC1 do not return fault if PLC2 is in STOP mode.

Does anybody have a good idea how can PLC1 know if PLC2 is in STOP mode? I do have one idea, but I am not sure if this is the right way to go, so I would like to hear some opinions.


Thanks in advance.

Use a watchdog flasher as part of the data you get.

There is several different ways to make watchdog program. This is one method:
http://www.birket.com/index.php/technical-library/52-reading-room/technical-library/81-watchdog

L D[AR2 said:

Use a watchdog flasher as part of the data you get.

Click to expand...

And the easiest way of getting a flasher is by activating the clock byte.

Alternatively you can use BSEND & BRCV blocks which are S7 communication but you have to code it in both ends.

But I think with PUT/GET if the partner is not available (i.e. partner in stop mode) then you get an Error from the PUT/GET blocks but the Error output of the blocks is set only for one cycle. Therefore sometimes if you don't latch the error you don't see it while monitoring.

You can also use the T_Diag block to diagnose a connection. It is quite easy.

Another alternative to PUT/GET, which is very easy to implement and diagnose is the I-device option. There is no need for code, the communication is Profinet (RT) and you can easily diagnose it with DeviceStates block.

Of course the old school way is to use a heartbit or lifebit. You send a 1Hz pulse from PLC2 to PLC1. In PLC1 you have a counter that resets from the pulse received from CPU2. If the pulse is not received the counter does not reset and at say 10 counts you can generate an error.

Hi all,

thank you for your responses, they have been very helpful. I have implemented watchdog flasher, and it works correctly.

@grnick50
I can confirm (using S7-PLCSIM) that PUT / GET do not set faults when parnter PLC goes to STOP mode, only if you turn of simulation completely. Error is not set even for a single cycle.