Step7 - 317-2 DP + CP341-1 or 317-2 PN/DP - which is better?

Our 315 is starting to look a bit like it's not man enough for the job it's being asked to do, so we're considering replacing it with a 317. In order to reduce the cost impact we're toying with the idea of using a 317-2 PN/DP which saves about half the price of the separate CP.

The first question is, does the PN sacrifice any of the functionality of the CP?

The other question is what is the difference in data throughput? I would expect that since the data no longer needs to transfer over the backplane at its snail-pace 180-odd kb/s that data transfer would be quicker. However, what happens to the system performance? Does the PN have a dedicated processor for the Ethernet port or does the CPU have to support it, possibly resuslting in poorer system performance?

Has anybody done any direct back to back testing?

If you are comparing the onboard PN port with a CP343-1 (not the LEAN model) then:

Yes you are sacrificing some functionality.
The onboard PN port only has S7 and TCP protocols, not ISO or UDP.

On the other hand, the onboard PN port is faster as the data does not have to pass through the serial backplane. And yes, there is a separate processor for the PN port.
(The only data comms that is handled completely by the CPU is the MPI-only port on some of the lower end CPUs. PN, DP and MPI/DP ports have a dedicated processor).

Thanks Jesper, that will help the customer make his decision.

By the way, during this discussion I saw the specs for the 319 for the first time - boy, that's a performance jump. I don't think it'll do the sales of the lower end 400s much good though!

RMA said:

By the way, during this discussion I saw the specs for the 319 for the first time - boy, that's a performance jump. I don't think it'll do the sales of the lower end 400s much good though!

Click to expand...

Siemens has just released (*) a new series of S7-400 CPUs that have integral PN ports and a significantly higher performance than the old CPUs. It looks like everything is moving a class up.

But yes, I have also looked at the 319, and it has supported me in my decision to go 100% with the S7-300 series from now on.
I think that it is relatively low priced for what you get.

*: Edit: They are ABOUT to release the new CPUs.

JesperMP said:

Siemens has just released (*) a new series of S7-400 CPUs that have integral PN ports and a significantly higher performance than the old CPUs. It looks like everything is moving a class up.

But yes, I have also looked at the 319, and it has supported me in my decision to go 100% with the S7-300 series from now on.
I think that it is relatively low priced for what you get.

*: Edit: They are ABOUT to release the new CPUs.

Click to expand...

Hello

The new SIEMENS S7-400 PN CPUs (not F-CPU) are the
CPU 416-3 PN/DP which is now as fast as the CPU 417-4 and the
CPU 414-3 PN/DP which is slightly slower than the CPU 416-2.

Result:
There is no faster CPU 400 than the “old” CPU 417-4!
Still all CPU 400 are slower than the CPU 319-3 PN/DP!
(Based on code execution performance, not I/O)

After waiting more than 2 Years, SIEMENS is now able to keep up with the competition with the CPU 319-3PN/DP in terms of code execution performance!