G120C DP Profibus Read/Write Parameters

Hi,

We have a G120C (6sl32101ke158ap2 to be exact) and we are trying to write or at least read these parameters via profibus:

P1001 - Fixed Setpoint 1 (W)

P1080 - Minimum Speed (Possibly R/W)

P1082 - Maximum Speed (Possibly R/W)

P2000 - Reference Speed (R)

P2002 - Reference Current. (R)

Is it possible? 

We have tried by setting the telegram to free (999) but these parameters are not showing on neither side i.e. transmit or receive. 

Note. As configuration software we are using TIA V15.1 U3 with Starter package.

Now for the second problem: 

First let me give you a small picture of our application.

We have this inverter as mentioned above. 

The drive can be set to manual mode by changing the command data set (CDS) and it can be controlled even manually.

When the CDS is changed it starts pointing to a new setpoint and all works fine.

Now when there is a power cycle and the plc does not turn on, that setpoint is lost.

Is there a way to save this setpoint so on power cycle is not lost or maybe another parameter that is retentive on power cycle?

Hi,

you can access those parameters by acyclic reading/writing commands from the PLC.

Therefore there are ready to use FBs available. Check out the SINA_PARA FB from the drive lib. Either you find it in the Global libraries of your TIA Portal already or you can download it from here:

https://support.industry.siemens.com/cs/ww/en/view/109475044

To the second problem:

I do not really understand that. As you want to access p1001 I think you are working with fixed speed setpoints (at least for one command data set). In case you have saved your drive parameterization retentively (copy Ram to Rom) this value should not change after Power Off/On.

What do you do when switching to another CDS? Where comes the setpoint from in this case? And what exactly is the problem then?

Hi thanks for the reply it really helped me with both problems. I am using SINA_PARA_S to read and write the parameters freely.

Is it better to use the telegrams or the fb. What would you suggest?

Should i just use the function block and just use the telegram for the status and control words?

Regards,

hmmm but with p971 you are completely right.

One important thing to know specially with SINA_PARA_S:

When you check the manual you will see that you need to use the input "ValueWrite1" and set it to "1.0" if you want to write a 1 to p971. This input is used for all parameter data types except DINT and DWORD -> p971 is just unsigned 16 data type. So this one is also written with ValueWrite1.

I would recommend to leave the "start" input to high for a while at the SINA_PARA_S FB. Can you see that the drive is doing something (LED blinking or so when you set this command)?

i solved it i had a bug in my program.

Refering to my edit question above?

Should i use the FB to write whatever i need and use the telegrams just for the status word and control word?

Regards,

Hi,

my personal general rule would be:

-Transmit as much as possible with the cyclic telegrams.

-Use acyclic communication just in case you have no access to parameters with telegrams.

The problem is the following:

You can only connect so called BiCo parameters (marked with BI:, CI:, BO:, CO:) to telegrams, those parameters are connectable. Other parameters which are not connectable can just be accessed with acyclic reading / writing commands. Cyclic communication is better for data that you want to see or change frequently. You can just change them each cycle in your program and they will immediately be active in the drive with each communication cycle of PLC/drive. Acyclic parameter commands are not usable for time critical data because you can never know when the drive accepts a written value or when you will receive a requested value from it. It can take up to maybe 100ms or more to refresh the value. So this type of communication is not discrete. You should use it only for data that is not changed or needed too often.

Hi,

I will read actual values and write  setpoints using the telegrams and other parameters which are not available on the telegram using the function block.

Thanks for your help