Terry,
Thanks for posting this topic. It was something I was considering posting yesterday. We are currently in the planning stages for a new controller and one of the features I am considering is online editing.
I would like to ask the forum if anyone has every experienced any problems with online editing.
Personally, I see potential problems with modifying code while the process is in operation...and therefore am extremely conservative/cautious about considering such a feature.
For any of you techies out there, just how would one design a controller that offers online editing? Our concept would be to have dual memory on the hardware side. Not quite certain how it would be performed in firmware just yet, in that we haven't researched it.
Based on the responses to date, it is needed most in process applications whereby the equipment is running continually. Many have stated that they don't need it, but it is nice to have..."a time saver"
I would think that once a machine is commissioned, the actual ladder code probably wouldn't be modified, but rather the variable information (timing), which can be done rather easily through an interface or PC. I would also think that to modify online while the process is running, one would have to be extremely confident in their programming abilities...one OOPS could cause major damage.
From a manufacturer's perspective, I would be offering a feature that if not used properly or used by someone with limited experience could make Entertron liable for damages. All the disclaimers in the world can't protect you...lol. Our basic view is that any new customer, whether completely new to PLCs or a pro, will have a learning curve with a new PLC, in that every ladder editor and features are different.
If anyone would like to enlighten me as to the nuts and bolts of online editing, I would be interested in learning more, so to be able to make an informed decision, for our new product.
"Adding cards on the fly"...are you referring to I/O cards or memory cards?
If we are talking about memory cards...I can see that in that some already do online editing. If we are talking about I/O cards...that would concern me.
In both cases, the manufacturer is presuming a certain degree of knowledge on the part of the customer. To change I/O while a process is in operation mode presents endless possibilities for disaster.
I look forward to participating further in the discussion.
God Bless,