S7: Wifi download = whole CPU in fault ???

Hi,

I have an issue with an S7 PLC when downloading over WiFi. It's a pretty big FB that I wanna download and the connection is poor. But it's well enough to monitor and download normally. When I download in full production it happens that the CPU falls out... all leds are blinking, no more connection or production... completely down because of an FB download ??

Any ideas about such issue ?

Thanks in advance,

Kind regards,
G

I am just guessing something here.
I assume that STEP7 generate a checksum for each block, and there are also error checking in each TCP/IP packet, so that the "connection is poor" can result in that many packets are rejected and have to be resent. Normally it goes OK, only you will experience long download times or varying monitoring speed. But occasionally, the checksum matches at both ends, despite that the block is corrupted and it slips through. That the CPU goes in a complete stop can be down to that it is the block type or destination info that gets corrupted.

Maybe your wifi router has statistics about the quality of the connection, or maybe info about how many bad packets that have to be resent. That can give you an idea.

Are you using Step7 (S7-300/400), TIA Portal (S7-300/400) or TIA Portal (S7-1200/1500)?

I'd guess it's TIA with 1200/1500, because for the same block code, it transfers about factor 100 more data than a S7-300 has needed, and uses bigger PDU sizes than a 300 (1024 - 240).

But the general concept of downloading a block is nearly the same in S7-300 and S7-1200/1500.

S7-300:
- PG gets some information about online blocks, PLC sends informations
- PG requests to download FB1 to passive memory
- PLC acknowledges this
- PLC request first chunk of FB1
- PG sends chunk
- if not the last chunk, PLC asks for next chunk until the last
- PLC sends that the block was received complete
- PG requests to copy the FB1 from the passive memory to active
- PLC response done
Then FB1 is active.

S7-1200 (same for 1500)
- compare online / offline
- PG says it wants to create a download sequence
- PLC answers if OK
- PG starts transmitting to download FB1 object in many PDUs (even the smallest block contain 3-4 PDUs of ~1000 bytes each). Only TCP acknowledge is used.
- PG says sequence is finished
I guess then the PLC makes the downloaded block active after this, as there is no explicit command to make the block active.

If it's Step 7 it could be classic that stat area or so have changed in fb.

spaderkung said:

If it's Step 7 it could be classic that stat area or so have changed in fb.

Click to expand...

That can cause an error, but not "all leds are blinking, no more connection".

Cpu

Hi,

It's a 317F-2DP CPU.
I download via the wifi all the time to PLC's. But this particular PLC failed twice allready in one week because of a wifi download. Maybe the CPU is loaded with more program code than the other ones, don't know...

However I also think it's because of the poor wifi. But the problem only occurs on that one CPU..

Thanks for the replies btw,
Kind regards,
G

All leds blinking means defective CPU.

Have you spare CPU for testing if problem goes away. Also looking diagnostic buffer afterwards can lead to error.

Is there enought memory available on CPU, it could be memory bottleneck, but the it should warns of possible bottleneck error before downloading.