Do-more Modbus/TCP Speed

[Mike Nash]

I am probably just missing this, but is the Do-more able to communicate with multiple Modbus/TCP slaves more quickly than the D2-260 with ECOM100?

From what I have "gleaned" it might take 4 scans or more per read/write to a slave for a total of 28 scans more or less for 7 slaves with the 260. Is this correct?

What would this be with the H2-DM1/E?

How about either Do-more and an H2-ECOM100?

I have a real app that is going to be the 260 & ECOM100 for sure at this point, but want to know my options for the future. I would like real-time control via ethernet but the ECOM looks rather slow.

Thanks!

[BobO]

I am probably just missing this, but is the Do-more able to communicate with multiple Modbus/TCP slaves more quickly than the D2-260 with ECOM100?

From what I have "gleaned" it might take 4 scans or more per read/write to a slave for a total of 28 scans more or less for 7 slaves with the 260. Is this correct?

What would this be with the H2-DM1/E?

How about either Do-more and an H2-ECOM100?

I have a real app that is going to be the 260 & ECOM100 for sure at this point, but want to know my options for the future. I would like real-time control via ethernet but the ECOM looks rather slow.

Thanks!

Do-more will be considerably faster, but without knowing the response behavior of your slaves, I can't give specifics. That said...no question...Do-more's on-board Ethernet port will be much, much faster for a number of reasons. The key thing is to create a dedicated Do-more Modbus/TCP Client for each target device.

There is a 0% chance I would ever use a DL260 for a comm heavy app if Do-more were an option. Zero.

[Mike Nash]

Thanks. The D2-260 is already there and programmed except for the Modbus/TCP comms. I would like to jump over to the Do-more but hate to do it on this application at this particular point in time. One more upgrade coming on this machine though and it may happen then when major PLC changes will be needed anyway.

I'm still trying to determine if the Do-more Modbus/TCP is going to approach AB Ethernet/IP speeds with third party devices. I realize we are talking substantial price differences and the AB is not a contender for this app, but where does the Do-more fall in the range between the D2-260 and the CompactLogix say? I'm only able to read/write 9 integers to each of 7 devices but would like to see each device serviced within 250mS worst case, though say 25mS would be far more desirable. This is a web handling app but at this point no real time updates are required though that would be preferable at the final upgrade.

[plcnut]

I know this doesn't specifically apply to your question, but I am perforrming http (tcp) requests over the Internet halfway across the country with a DoMore in the sub-second range.
I say that to say that the DoMore is quick, and GREAT with comms.

[BobO]

OK, I put together a simple test. I have an H2-DM1E talking to a T1H-DM1E using 7 parallel client devices. Each client is doing a single MRX of 10 holding registers. Each client is averaging around 85 updates per second, or roughly 12ms. Do-more may be inexpensive, but...

[Mike Nash]

Thank you for doing that test. It answers my question quite well. BTW, I was not trying to compare the two products, I am well aware that price does not always reflect capability nor indicate superiority. I just needed to get some idea of speed vs something I have used recently.

We do intend to get a do-more for training ourselves. I will not have access to the hardware on site in a manner timely enough to feel comfortable enough with translating. It has terminator CTRIO, terminator analog and digital I/O, rack I/O, Cmore and now Modbus/TCP to 7 drives along with leaving an existing GE 90/30 handling the drives via analog and discrete. I hope to switch the 260 to Do-more later next year. This phase came down the pipes with no warning.  And I still use DS3 as it allows small icons. UI tends to be important to me but more in a get out of my face with your dime store trinket icons eating up my precious real estate type reaction.

[BobO]

Thank you for doing that test. It answers my question quite well. BTW, I was not trying to compare the two products, I am well aware that price does not always reflect capability nor indicate superiority. I just needed to get some idea of speed vs something I have used recently.

ADC recently quoted a major system for a large end-user. The price was 1/3 that of AB and had already been prototyped and proven capable by the company's own engineering staff...and yet the guy who was making the decision was struggling to believe that it could do the work, even while watching it do so. "Too cheap" he said. Never heard whether we got the business in the end, but he was willing to pay 3x more for the illusion of quality.

We do intend to get a do-more for training ourselves. I will not have access to the hardware on site in a manner timely enough to feel comfortable enough with translating. It has terminator CTRIO, terminator analog and digital I/O, rack I/O, Cmore and now Modbus/TCP to 7 drives along with leaving an existing GE 90/30 handling the drives via analog and discrete.

Do-more's built-in Ethernet I/O support makes the Terminator I/O appear as local to the Do-more CPU. Even the CTRIO is supported natively by Do-more's CTRIO instructions. You will not believe how much easier it is, even than DL with IBoxes. When you finally do make the change, you won't regret it and you won't go back.

And I still use DS3 as it allows small icons. UI tends to be important to me but more in a get out of my face with your dime store trinket icons eating up my precious real estate type reaction.

One of the Do-more support techs at ADC runs Do-more Designer with tool bars completely off...no icons at all...and gets by quite nicely. You're not alone.

[Controls Guy]

OK, I put together a simple test. I have an H2-DM1E talking to a T1H-DM1E using 7 parallel client devices. Each client is doing a single MRX of 10 holding registers. Each client is averaging around 85 updates per second, or roughly 12ms. Do-more may be inexpensive, but...

600 Modbus transactions a second!  VERY impressive! 

Try changing the register count per request to 100 or something at the larger end of the spectrum, so we can derive the relationship of requests per second to request size.

Very, VERY cool!

[BobO]

At 1 word per slave, it sits at roughly 86 transactions per second per slave.

At 100 words per slave, it drops to about 80 transactions per second per slave.

Not terribly scientific though. Network load and PLC scan time will greatly affect these numbers. The takeaway should be that Do-more does comm pretty well.

[Controls Guy]

Yup, that and the fact that speed is more transaction-count and scan time than register-count dependent.

Do-More doesn't repeal the conventional wisdom to exchange as big contiguous blocks as possible per transaction.