I can't figure out what I'm doing wrong with regards to the Modbus Control Word (STW) to the V20 in TIA Portal 14. 

I am trying to run the motor by setting the bits according to the HMI screen that Siemens provides in their example project, and also understand what is going on with the V20.

Exactly how do I read and write the status and control words? 

I went online on the PLC and took these screenshots:

1. Online TIA Portal 14 hardware configuration.

2. Online CM1241 modbus module settings in TIA portal.

3. Online Modbus block made by Siemens

4. Watch list with control word and status word. 

5. Screenshots of the Siemens manual on Modbus control and status word.

Please see attachment.

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Split from V20 no speed from modbus (receiving but not running).

AutoGen_6899965

I have a similar issue, I just can't figure out what I'm doing wrong with regards to the control word to the V20. 

 Can you be more specific about the issue you're having with control word STW.

You are showing two networks dealing with STW, one reads and one writes.

1- Are you able to read STW from the drive?

2- Are you able to write STW to the drive?

TechTeam

Hello,

please check your drive.
Status word looks like a fault condition is active on the drive.

 Hey TechTeam and Kal.A, can you give me a hint on which direction to read the bits in the control  and status word?

Do I read from the 9th bit from the right and then the left?

If so, then yes I see fault is active. 

I will be in front of the V20 tomorrow, but right now I am trying to make sure the Modbus communication is working properly so I don't have big issues tomorrow. 

We have already set the V20 settings according to the manual over the phone, but I might just factory reset it tomorrow to make sure everything is set up correctly. 

What do I do to make the motor run? Set the bits according to that HMI screen and then set bit 0 high in the control word?

Please advise.

Kal.A

 Can you be more specific about the issue you're having with control word STW.

You are showing two networks dealing with STW, one reads and one writes.

1- Are you able to read STW from the drive?

2- Are you able to write STW to the drive?

 I just wrote 2#0111_1110_1000_0100 to the STW and it automatically changed to the last bit 15 back to 0. So apparently yes, I can write the STW and read it also. But status word doesn't change. What exactly do I write to the STW to make it run? 

Ok I just read the bits from the right. So I got to send the drive 47e and then 47f (according to other post in forum). I managed to make it turn but it only ran for about 10 seconds at 30hz. Then it slowed down to a halt and gave all the three last bits of the status word as errors which doesn't make much sense to me right now. 

I'll be sure to check what the drive itself gives as error message. 

I was in front of the V20 today and it ran for about 10 seconds and slowed down to a halt again. It showed fault F72. According to Siemens that fault is Modbus/USS Setpoint Fault.

I googled the error fault and randomly came across a youtube video comment saying to change the inverter parameter P2014 Slave Timeout from the Siemens Modbus Documentation recommended 130ms(Connection11 Modbus default) to 2000ms (Factory default). The fault no longer appears.

It seems to run but we didn't want the pump to run dry for too long, so we will have to do some more testing. Is 2000ms as slave timeout ok? 

The status word is read by Siemens' own TIA Portal 14 S7-1200 Modbus V20 project, so I don't see how it should be twisted in the PLC?

I think the status word is showing correct now, but I can't know for sure because the V20 is in another city - though I think we have enough to do the final wet tests soon.

TechTeam

Hello,

Please check the fault messages on your drive sounds like a fault become active.
Make sure that you read the status word correct and it isn`t twisted in the PLC.
The last three bits would only make sense to me when bits 5 = OFF3 active, 6 = ON inhibit active ,7 = Inverter warning active  are shown as last bits due to any shifting operation.

Please compare the status word shown by the drive with the one displayed in the PLC to identify differences.