Modbus question

[belae1ka]

I am currently trying to change communication protocol settings for my VFD;

This is the parameter memory address to change communication protocol settings (from manual);

In the VFD manual it states that three different types of messages are typically sent to GS Drives;

1)Read Registers

2)Write Multiple Registers

3)Write Single Register

To change the parameter in the image above I plan on writing a single register.

Here is the format to do so (from manual);

This is where I get confused... I am using a Modbus library that I downloaded from JKI package manager and I am confused as to how to send the command message.

Shown here is my overall block diagram (so far);

When I  view the block diagram for "Write Single Holding Register.vi" this is what I see;

I need to input two things to change communication protocol settings;

1) Parameter memory address. In U16 format would this be "0902" ?

2) Data to write. In U16 format would this be "0003"?

In the block diagram;

1) Would "address" be the parameter memory address?

2) Would "register to write" be where I input the data?

Thank you for your time.

[RavensFan · Accepted solution]

1.  Yes.  Address is the parameter memory address.  If the constant or control is in decimal display, enter 2306.  I would recommend putting it into hex display and enter 902.  Which like I said in other messages is easier to see that you are writing to 9.02.

2.  Yes register to write is where you put the data.  So put in 3.  In this case it won't matter if it is in decimal or hex display.

However, go back to what I said in my last message in the other thread.  The API's seem to hardcode in a 1 for Stop bit.  Or at least is is not visible in the purple header modbus API.  Parity defaults to even since you don't have a constant or control wired into the parity input.  So you really should use choice 4,  even parity, 1 stop bit.

[belae1ka]

You are a lifesaver RavensFan. I can't thank you enough!