MB_SERVER Function 23 clarification

Good day all,

The 'F1 help' manual states that Function 23 is supported by MB_CLIENT as of V6.0. It does not state anything about the MB_SERVER block.

For clarity, does the MB_SERVER block support Function 23?

Thanks,

A

Hi Aleech

Regartin STEP 7 V17 manual, it seems as if it is supported.

https://support.industry.siemens.com/cs/ww/en/view/109798671/141152774027

Br,

Cocolino

Thanks Cocolino, I hadn't spotted that hidden in there.

This then brings me to the next part! For some reason, I can use:

An MB_CLIENT configured as mode 1 (Write reg) with start 40001 and length 10

An MB_CLIENT configured as mode 0 (Read reg) with start 40011 and length 77

Both on an individual basis work absolutely fine. As soon as I move the settings to be mode 123 and put in the relevant parameters, the blocks try to talk, but flit between statuses 7005/7006 (good!) and 8383 (Bad). No data is actually written or read from the relevant data areas at all.

8383 is usually bad data length or area, however from testing individually, we know this isn't the case!

I should clarify I am using 2 separate PLC's, one a 1500 and the other an ET200SP.

Any ideas why we would be seeing this kind of behavior?

Thanks!

Hello,

I expect some not correct blocks handling. In case (I expect that) you have only one connection created (one Server) you can use at one time only read or write function to register. It means, if you have 2 Client blocks, you need have one working and other disabled. To do this, there are Disconnect and REQ inputs. It's not clear what you really do in your code but you probably mix functionality of blocks in same time. Try do logic in your code to have REQ not set true on both blocks at same time becaus ethis can be your problem. Set initially both blocks as Disconnect, REQ to false and then via some state machine code do independed connect and REQ (start poll) to do your jobs. After one (read f.ex.) do disconnect, check all is ok and then Connect next Client block (wrie), check connected and set REQ to true, next job will start. You need carefully differ both functions (read/write).