Wonderware DASABCIP ENBT-DH+ Update Rate

Hello All,

I have a PLC-5 sitting on DH+ network connected to Wonderware HMI through Logix5000 ENBT-DHRIO Bridge. HMI polls over DASABCIP.

The topic has 4500 tags, 89 messages in DASABCIP. DH+ network is 57.6 kbps. It take up to 15-20 seconds to poll all 4500 tags which I believe is really slow.

Can you, please, provide any statistics from your networks, how fast is your poll rate for what number of tags/messages? What do you think about 4500 tags takes 15-20 seconds to poll on DH+ - is it OK or really slow?

Thanks a lot.

I would not describe 4500 tags in 15-20 seconds on a DH plus network as slow.

Hmm, how about: DASABCIP server polls 4500 tags in 89 messages which are packets to me (maybe I am wrong here?).
So 89 packets to poll 4500 tags. A packet can be 500 bytes max, the speed is 57.6 kbits/s = 7.2 kbytes/s ==> 12 packets per second (with all system info).
Then 89/12 = 7.5 seconds to poll 4500 tags in ideal world. Plus there is some other traffic in DH+ network.

So I would be OK with 10 seconds, but 15-20 is too much to me.

Am I wrong somewhere? Any real results from other people, please?

Thanks a lot!

Its been a long time since I worked on PLC-5 on DH+.
As I mentioned in my previous post, I do not think your update times are out of wack.

DH+ is a token passing network, so any device can hold the token for a finite amount of time or data transfer. I seem to recall the data size as being around 240 odd bytes.
You do not mention how many other devices are on the DH+, this will have a big impact. The theoretical max number of stations is 64, the practical is 24-30. Also what are the other devices (PLC/HMI)
The system will also scan for new or missing nodes, this adds to the token rotation time.
Your data has to go from the server to the ENBT, through it to the DHRIO, the DHDRIO has to get the token send the message. The PLC-5 (not the fastest PLC), has to construct the reply, get the token then send the message back through the path.

Assuming your physical DH+ network is perfect, this happens with out errors or retries. Have you inspected the DH+ cabling / routing / installation.

AB has a manual DH/DH+ Protocol and Command Set (Or something similar) that explains how the token gets passed and the size of the message packets.

Remember DH+ / PLC-5's are 25 year old or older technology!

Hello Mike,

Thank you for the reply.

To my understanding there are 3 PLC-5/SLC-5 PLCs on DH+ network + ControlLogix 5000 with ENBT Bridge. There are MSG instructions in Logix 5000 over DH+ and ENBT, but the instructions are called every 5-10 seconds.

I found that there are two DA Servers. They are supposed to be redundant, i.e. one polls the data, the seconds is a standby and polls just 1 item, but it is polling more than that. I am going to install an update for Wonderware to fix the redundancy issue, but I am not expecting a big improvement after that anyway.

Thanks again for you experience sharing.

If anyone has other numbers for DH+ communication from your own experience, please, let me know.

Thank you.

After doing some tests on VMWare player limiting my Ethernet speed to 28.8kbps download/upload I got pretty much the same update times as the client has on site.
An update time for 5600 optimized tags took about 7 seconds at 57.6kpbs speed. The clients data is not optimized that is why it is doubled here + some other MSG instructions executing between the PLCs.