Questions about BRX?

[Mike Nash]

I was told to order a BRX starter kit today and I didn't even have to ask! A customer had one and he was enthused.

But I am going to get a BX-DM1E-36ED23 instead I think. I really want to play with the Axis instructions and the 6 "free" analog points are really appealing with the bipolar ins and outs.

I am wondering about the 1 Mbps throughput maximum note on the optional Ethernet POM (BX-P-ECOMLT). What kind of hit would that be for an HMI or three in the real world? I am suspecting not much, but would like a more knowledgeable answer.

[BobO]

I am wondering about the 1 Mbps throughput maximum note on the optional Ethernet POM (BX-P-ECOMLT). What kind of hit would that be for an HMI or three in the real world? I am suspecting not much, but would like a more knowledgeable answer.

Hit? To PLC scan time? Or HMI performance? And if HMI, what HMI and protocol?

[Mike Nash]

HMI(s) would be Cmore with Do-more Ethernet protocol.

I'm simply wondering if the refresh rate (performance) on the HMIs (lets say three of them) would be significantly slower on the POM than on the built-in Ethernet port.

And since you mentioned it, would the PLC scan time be different due to HMIs on POM versus built-in Ethernet?

[BobO]

HMI(s) would be Cmore with Do-more Ethernet protocol.

I'm simply wondering if the refresh rate (performance) on the HMIs (lets say three of them) would be significantly slower on the POM than on the built-in Ethernet port.

And since you mentioned it, would the PLC scan time be different due to HMIs on POM versus built-in Ethernet?

For programming status, I don't notice much difference between the onboard port and an ECOMLT. I haven't studied it from the perspective of an HMI, but I'll check the maximum transaction/point rate and see what I get.

There is soon to be a new Do-more driver for C-more, a symbolic driver that passes element names, like "X5" or "T0.Acc", that will be more flexible, but slower for both C-more and PLC.

The POM port hit to the PLC is significantly lower than the Ethernet port. The IP stack is a pig, and on the ECOMLT, all of the IP stack is handled by the module.

[BobO]

I opened a bunch of data views and trend views in DmD, and was seeing about 100 transactions per second and 2000 items per second. It would probably go higher. Don't know much about C-more's comms, but unless the HMI pages are crazy complicated, I would think your updates would be very crisp.

[Mike Nash]

Thanks for checking that. It's always good to know something won't catch me out!

When you say the IP stack is a pig, are there any situations I should be on the lookout for that when using the built-in Ethernet port?

a symbolic driver that passes element names, like "X5" or "T0.Acc"

I think I understand the T0.Acc example, but the "X5" seems like something we can already access or is it not? Hopefully I'm not being dense on this, it's just that sometimes the example given for something is ambiguous enough that while true, it does not give an answer that can't be misconstrued - for example, how hex numbers work: 0x4 + 0x3 = 0x7 instead of 0x5 + 0x6 = 0xB.

[Controls Guy]

When you switch from a completely table-based memory architecture to partly or wholly heap/tag based, the location of a given element is no longer defined by it's "address", so you have to pass the name.  Sounds like C-More was using Do-More protocol, but probably only had access to table memory areas (maybe even no access to user defined tables), and perhaps some built-in heap items.  I assume they're doing this to allow C-More access to user heap items (and possibly user table/array data as well).

[BobO]

They have access to *everything* using the native programming interface, but chose not to deal with the complexities of a translation table for a dynamically changing memory map. The native programming interface is designed to be very high performance, but does require you to convert from human readable element names to numerical definitions.

The symbolic driver uses a new interface that eliminates the translation, or more to the point, offloads it to the controller. I personally consider that to be a horrible design choice, but in the end, it was the only way we were going to be able to get C-more support to the level it needs to be.

When I say the IP stack is a pig, I just mean that it bumps the scan time far worse than I would prefer. You won't get in trouble. The controller is quite capable of protecting itself.

[Evilbeard]

Are there future plans to give us a BRX simulator? I've been wanting to fiddle with a few things on the Axis controls, but it tells me that they aren't valid commands with the simulator.

[BobO]

Maybe. Some of this is software, but big chunks are hardware functions in FPGAs. Not the easiest to do, and we still have a very long list of things to get done.

[Mike Nash]

Are there future plans to give us a BRX simulator? I've been wanting to fiddle with a few things on the Axis controls, but it tells me that they aren't valid commands with the simulator.

I would like to see this too. I realize the ROI might be a little meager though from Host's standpoint.

Still, the high speed stuff would sure be nice to play in a simulator with. (Our 36 pt (42!) should be on the way.)

[BobO]

I'm honestly not that concerned about ROI per se, it's more about the best utilization of limited design resources. So many targets, so little time.

[davidbgtx]

Quote BOBO - There is soon to be a new Do-more driver for C-more, a symbolic driver that passes element names, like "X5" or "T0.Acc", that will be more flexible, but slower for both C-more and PLC.

I am confused by this too, I thought it was already passing element names like t0.acc and t0.timing, or are we only talking brx? My pics are from DM1E

[BobO]

I'm talking about the protocol itself. C-more has had native support for Do-more for a while, but the support was limited. The new symbolic driver uses new protocol functions that we added to Do-more 2.x firmware for all platforms. Unlike the previous driver, this one passes textual symbol names on the wire, and allows access to everything.

[davidbgtx]

Sooo, I could stick with the old driver and avoid the hit on the scan time? Or am I being overly cautious?