Hi,
if you send a request, a response is needed. If no response is received in parameterized monitoring time, then an error message is shown on ERROR and STATUS. The output parameters are shown only 1 plc cycle. Did you save the outputs DONE, ERROR and STATUS to check, what is shown this 1 cycle?

Could you attach the online IDB of the modbus block?

Best regards,
Wüstenräuber

Which bit you try to reset? 
You start a telegram with a positive edge to ENQ_ENR. After start you have to set the bit to FALSE. It is only a positive edge, not a positive level.
When you start a telegram with ENQ_ENR (or ENQ), then there is always a result: either DONE = TRUE, if it is successful or ERROR = TRUE, if it is not successful.

Can you attach the project? It seems that the call/handling of modbus block is not correct.

Without more infos it is not possible to find the reason. You could attach a screenshot of the OB, in which the modbus block is called. 

Which values do you parameterized for RECV_TIMEOUT and CONN_TIMEOUT?

The parameters are not correct. 
You have to delete the comments before ENQ_ENR:
A “CONTROL_DAT”.ENQ_ENR
R “CONTROL_DAT”.ENQ_ENR

And you have to set ENQ_ENR, when DONE_NDR or ERROR are set. (not reset)
O “CONTROL_DAT”.DONE_NDR
O “CONTROL_DAT”.ERROR
S “CONTROL_DAT”.ENQ_ENR

Please have a look at the manual or the block online help how the modbus block works. 
You have to set ENQ_ENR to TRUE to start 1 modbus telegram. After calling of modbus block with ENQ_ENR = TRUE you have to reset ENQ_ENR = FALSE, because the modbus block needs only a positive edge to start the telegram, not a permanent signal. 
That is why you need these lines below the call:
A “CONTROL_DAT”.ENQ_ENR
R “CONTROL_DAT”.ENQ_ENR

During the modbus block works, BUSY is TRUE. When the telegram is finished, DONE_NDR or ERROR are set for 1 PLC cycle. 
If you want to see these bits more than 1 PLC cycle you have to save it in another memory or you increase a counter. Also the STATUS output should save into another memory area, if it <> 0. 
Have a look at the original example project. In this project the handling is programmed.

If you want to start the next modbus telegram, you have to set ENQ_ENR = TRUE:
O “CONTROL_DAT”.DONE_NDR
O “CONTROL_DAT”.ERROR
S “CONTROL_DAT”.ENQ_ENR
But you may only set it to TRUE, after the previous telegram was finished.
 

You can also attach the online IDB of the modbus block. Then I can have a look at the internal parameters.

Hi,
change the parameter for “connect_startup” to FALSE in parameter DB and re-initiate the modbus block. I know, that sometimes it is a problem with communication partner, if this bit is set to TRUE at start. 
(If the connection is not established, when ENQ_ENR is set to TRUE, then the connection establishment is initiated automatically. That is why it is not a problem to set this parameter to FALSE.)

Wüstenräuber

Attach a new picture of the modbus block call in OB1 and the onlineIDB as pdf. 

When you open the OnlineIDB of the modbus block, you can print the IDB as pdf. It is more easierer than screenshots. ;-)

“connection at startup” is still TRUE. Change it to FALSE an re-initialize the modbus block. This is an init parameter and is only taken over, when the block is initiated.

Did you re-initialize the modbus block? In online IDB this internal parameter is still TRUE. Attach the new online-IDB as printed pdf.

Without the complete Online-IDB it is hard to find the reason. DONE and ERROR counter are 0, so no telegram is handled. 
What happens when you set ENQ_ENR = TRUE now via VAT? In STATUS there must be a change. 
Do you also use the connection ID = 1 for another communciation function? ID must be used only for this one modbus block, for no other block. Can you attach the wireshark-Trace of the telegram (query and response)?

Strange port numbers… Normally the modbus server has port number 502.  It it seems this is not a modbus telegram, I can't see the modbus header…
Please attach the parameter datablock. 
You can also copy the modbus block, the OB1, the online datablock and the parameter datablock into an additional project, zip and attach here. 

I need the information in the Online IDB of the modbus block and in the parameter DB. To make screenshots of all pages is to time intensiv, I think. So the idea is, that you copy the online blocks into another project to send me.
If you have time, you can also make many, many screenshots. ;-)

Almost… :-)
You parameterized the modbus block as a client (active partner), so you should make screenshots from “iMOD_CLI…”, not “iMOD_SERV”. It is sure, that the communciation partner is parameterized as a server?
And please a screenshot from online parameter db from adress 130.0 (ID1_send_buffer - 1 page) and from ID_recv_buffer. Then it is possible to see, if any byte is sent and received.

Check if TSEND is a part of your project and has the correct FB number. I don't see any action of TSEND. In properties of the modbus block you see, which FB numbers are called. These FB numbers must be used for TSEND, TRCV and so on. If you use another FB with the number of the TSEND block, which the modbus block calls, then it doesn't work.

FB numbers and symbols must be the same like in the modbus block property. When you change the names or the FB numbers, that you have to rewire the FBs in the modbus block. Have a look at the manual, there is a chapter for rewiring of the internal called blocks.

yes, both has to fit. In chapter in manual it is described too

The best way is, to copy all modbus blocks and T blocks from the example project into another temporary project, rewire as described in manual and than copy all of these new blocks into your project. So it is sure that you don't change the existing blocks, which you are using in other OBs or FBs.