S7-1500 Ethernet Comms to S7-300

[beethoven_ii]

I have set up comms between an S7-1512SP-1 PN plc programmed with TIA v17 and an S7-314C programmed with Simatic S7 using GET and PUT blocks in the S7-1512 cpu. There is an existing communication set up with another S7-315 plc using GET and PUT blocks which works fine. Both communications have been done using an S7 connection to an unspecified partner. I have a watchdog counter between my 2 plc's and it works but regularly stops communicating every minute or so and takes anything up to 2 minutes before it starts working again. Sometimes it restarts quicker but the timing varies. I realise there may be site network issues which may be contributing to the problem but on continual ping from a command prompt I can connect to either plc in 1ms or less on a regular basis. All the settings in my new S7 connection look the same as the existing one that works, other than the hardware ID which is of course different.

I'm just wondering any anyone has had similar problems and found a resolution in comes between an S71500 cpu and an S7-300?

 

[Lare]

Can it be false alarm?

I mean that that coms actually work but alarming have changed as 1500 code runs faster?


How coms alarm is done?

 

[beethoven_ii]

There is no alarm. I have 2 watchdog values in a DB. When the values are equal I increment the 1st value in the S7-1500 plc and send it to the S7-300 plc. When the S7-300 detects the watchdogs have different values it copies value 1 to value 2 to to make them equal and sends value 2 back to the S7-1500 plc. When the S7-1500 detects the values are equal the process is repeated. This works fine and updates every 1 second for a period of time and then it stops updating and the S7 connection goes red when I monitor it in the network connections of the plc. It does recover but how long it takes seems to vary.

 

[RVaughan]

When are the GET and PUT called, and how often is the REQuest made?
If I remember correctly, those blocks have issues if a request is made while they are busy, so adding logic to prevent that would be prudent.

Are the instructions outputting error codes?

 

[beethoven_ii]

I have a flash delay on and off timer in the plc which pulses on and off every 1 second. I activated the REQ for the GET block when the delay on time was done and the REQ for the PUT block when the delay on time was not done. After wasting a lot of time trying to get this to work on a live production line I found a way around my problem.

There were already GET and PUT commands in the S7-1500 to another s7-300 PLC on the same network which was working without any issues. I tested a new S7 connection with GET and PUT blocks between the S7-300 plc used in that connection and the one I was looking to add a connection to and it worked perfectly. I have now piggy-backed onto the existing working connection between the S7-1500 and the other S7-300 and managed to route the data I need through that and I use a GET block to copy the data I need into my other plc. I may do some testing on this when I get back to the office using an S7-1200 I have and an S7-300 to see how I get on.