Hi all -
Considering using S7 GRAPH for some sequencing. I have a few questions which I am having difficulty finding clear answers to in the Siemens documentation. I have experience using SFC on AB / RA systems but there is a bit of a learning curve to Siemens.
I could likely program everything I need in ladder much quicker but trying to a) learn something new and b) GRAPH may arguably be easier to troubleshoot for complex sequencing, so I'm thinking a bit about future ease of maintenance.
1. I've heard GRAPH takes a toll on scan time. For a S7-1515 CPU (working in TIA Portal v18) in a process control application, would this be something to be overly concerned about?
2. Can another GRAPH routine be called from within an Action? For example, Step 5 Action of fbSequence1 calls fbSequence2. The alternative seems to be to just create a new sequence inside the original FB but it "feels" more modular to have another block per sequence.
3. If I interrupt a GRAPH sequence (before it reaches the end), can I automatically resume at another step other than the Initial Step? If not, is there is built-in means to track active step, or should I just create a "CurrentStep" tag and update it programmatically?
4. Similarly, if a GRAPH routine is interrupted, how difficult is it is to re-initialize to avoid any "weird" behavior if I re-call the sequence?
Thanks.
Considering using S7 GRAPH for some sequencing. I have a few questions which I am having difficulty finding clear answers to in the Siemens documentation. I have experience using SFC on AB / RA systems but there is a bit of a learning curve to Siemens.
I could likely program everything I need in ladder much quicker but trying to a) learn something new and b) GRAPH may arguably be easier to troubleshoot for complex sequencing, so I'm thinking a bit about future ease of maintenance.
1. I've heard GRAPH takes a toll on scan time. For a S7-1515 CPU (working in TIA Portal v18) in a process control application, would this be something to be overly concerned about?
2. Can another GRAPH routine be called from within an Action? For example, Step 5 Action of fbSequence1 calls fbSequence2. The alternative seems to be to just create a new sequence inside the original FB but it "feels" more modular to have another block per sequence.
3. If I interrupt a GRAPH sequence (before it reaches the end), can I automatically resume at another step other than the Initial Step? If not, is there is built-in means to track active step, or should I just create a "CurrentStep" tag and update it programmatically?
4. Similarly, if a GRAPH routine is interrupted, how difficult is it is to re-initialize to avoid any "weird" behavior if I re-call the sequence?
Thanks.
