Brain vs Controller

I am a total newbie to OPTO22 but not for PAC’s DCS’ & PLC’s. Just recently inherited a customer that is using PAC systems R1 controllers and EB-1 Brains. They have given me the downloaded strategy file and claimed it was downloaded from a EB-1 Brain module.

That cannot be right, right?

I thought Controllers held the Strategy files and Brains were simply I/O processors. Can a strategy file be loaded on to a Brain?

Next Newbie Question:

In the OPTO world, How are I/O Status from a brain module gets sent to the controller and finally to an HMI?

Rack1:[ Brain / IO] ------ENET--------> [RACK2: Controller + I/O]----ENET–> [HMI]

Is the Above correct?

How are the I/O status from Rack2 Sent to Rack1 or from Rack1 to Rack2? (Where do I look in the strategy file to find out how this is done)


Hi Skyfox,

Welcome to the forums! Sounds like you’re not a total newbie, you’ve got a good handle on the pieces already.

If you could give a few more specifics to make sure we’re on the same page, that would be great. When you say “downloaded strategy file” what do you actually have? Is it the compiled “control engine download file” (a single file with the extension .cdf)? Hopefully they gave you an entire PAC Control “archive” (a zip file with a number of files in it that make up your whole “strategy”).

Either of those would require a controller to run (in a PAC-R like you mention, or one of our many other controllers, including the PC-based one we call SoftPAC). Click here to see form 1677 that gives a full comparison of brains/controllers. For a higher-level overview try [URL=“”]this flash interactive demo on SNAP components. The PAC-R is a special since it’s both a controller AND and I/O unit, as you correctly indicated on your diagram.

Brains are not exactly simple I/O processors (they can run 96 PID loops, and do other I/O features like totalization & counting), but you’re correct, they can’t run a strategy. Also, those features are much easier to set up in strategy you’ve created (or inherited, which happens a lot) using our PAC Project Suite – specifically PAC Control for the strategy.

On your HMI question, the short answer is: yes. Usually the tags created by your strategy (including those for I/O) are what’s referenced in the HMI. However, our PAC Display (free!) HMI software also has an option to access I/O directly. We also have some (older) brains that connect to controllers via RS485. Guessing that’s not what you’re asking about, though.

FYI, our new groov Box also uses that same tag database to help you create browser-based (including mobile) HMI screens.

What HMI do you plan to use?

For your last question, assuming you have the whole strategy, you could open it in PAC Control and look in your strategy tree at the bottom under “I/O Units.”

I’m guessing/hoping you’ll see 2 there, one for the “local” I/O on your PAC-R1 (IP Address likely to be meaning “talk to self”), and a second one for that EB1. The controller part of the R1 communicates with it’s own I/O and the EB1 I/O in the same way (via the memory map, but you don’t need to worry about that if you’re using PAC Control).

Hope that helps get you going. FYI training and [URL=“”]support are free! We’d love to have you join a class here in Temecula, CA.


Thanks OptoMary,

Your detailed response was very much appreciated and was extremely helpful. The customer I am dealing with is not familiar with the system they have as they inherited it from a third party. I was initially told the OPTO-22 Software rev was Rev.9. So I went ahead purchased the PAC project Pro from OPT-22. Upon opening the back-up sent by the customer, it prompted and said it had been created with an earlier version (8.xx). Now I am in a bind. I do not want to upgrade firmware on customer site and want to keep the revision as is. I also don’t want to shell out another 1000.00 to buy rev 8 PacProject Pro. What are my options at this point to make some minor changes to this existing code without changing rev8 to Rev9?

To answer your question, I did receive the entire backup, and the entire system was done using OPT-22’s PAC Software(HMI) /Hardware.

Can Both versions of PAC Project “rev8 & Rev9”, be installed in the same computer at the same time?

If a brand new HMI application was created using Rev9, will it still support Rev8 Hordware?

Thanks Again and Best Regards


Although it’s not “officially” recommended/tested, if I were you, I’d just use the 9.X software – it’ll be fine w/your 8.X firmware (until you want to use a command that was added [I]since[/I] 8.X firmware, like the 9.X PAC Control command “SendEmail”). No need upgrade until you [I]need [/I]something in the newer firmware.

PAC Project 9.X has some nice improvements in PAC Control/Display you could use. For example, searching for tags is easier in PAC Control 9.0 and newer. That’s very important when you’re trying to sort out what a strategy does when you’ve inherited it.

You can have both on one PC. I have several versions of 8.X and 9.X all existing happily on this PC.

A new 9.X HMI (PAC Display) should be fine w/your 8.X firmware, although [I]groov[/I] requires 9.2 or newer.

Was it 8.5 firmware you have? I can think of at least one big application where we have a customer using 8.5 Firmware w/9.X PAC Project and it all worked perfectly.

Hope that helps!

Hi and Thanks Again,

It Came out as R8.2C.

I am a bit concerned about Mixing Rev 8 & 9 as I do not want to inherit additional issues from the custormer. Is there anyway I can downgrade to rev 8.2c?


No problem. Just contact support (best via email: for instructions on getting 8.2 PAC Project.

Couple of quick questions…

Say I recompile R8 to R9 and download R9 in to the controller with Rev. 8 firmware.

Day’s later someone else tries to upload a back-up from that same controller using Rev8 PacProject.

Will that be allowed?

Will the rev Say 8 or Rev 9?

I am assuming PACPROJECT is the only program that controls Strategy Revision numbering, and it is never changed by a controller.

Am I correct in that assumption?


Your assumption is correct. Once your strategy is opened (and saved) in a newer PAC Control version, you can’t go back. The controller can tell what firmware version is running on it, but won’t complain until you load a strategy that includes a command it does know yet. Hope that makes sense!