HOW CAN I USE MODBUS RTU WITH ASCII TO CONTROL VFD.

BECAUSE SOME INVERTER USE RS 485 ASCII .

Hello,
Modbus RTU and Modbus ASCII are two different things.
Even the frame sent over de wires is different (number of bits per char for instance).
See SimplyModbus explanation.

In other words, you do not use Modbus RTU to emulate Modbus ASCII.
You need something that supports Modbus ASCII from the start.

A possibility is: a loadble driver for modbus ASCII master configuration:
CP341 Loadable Modbus ASCII (16 bit & 32 bit) Master Driver

Pay attention: The link says that the ASCII Modbus Driver does not support the new CP's with order number: 6ES7341-1.H02-0AE0

Have also a look to the FAQ CP340/CP341 Multi-Station polling based on ASCII driver protocol

There is no way to use Modbus RTU to connect to any device that does not use the Modbus RTU protocol.  There is no way to use Modbus ASCII to connect to any device that does not use the Modbus ASCII protocol.

If the inverter's documentation does not say "Modbus ASCII" then it does not use Modbus ASCII, it uses some proprietary ASCII protocol. 

It appears as is the 3rd link in JKLM's reply might be a generic ASCII module which might support your custom programming to match the drive's ASCII.

pls be clear about that ASCII, you mean MB ASCII or implement user defined ASCII protocol frames to RTU? This is important.

Hello,

very sry, I don't still understand what you want to do. Does your VFD use Modbus ASCII protocol or Modbus RTU protocol or simple ASCII protocol? Hope you understand this problematic.

Update: sry but don't post same question to next topics, this can be chaos to correctly answer your question. I saw from your another post that your VFD use Modbus RTU protocol, so you can use this example as start and study:

https://support.industry.siemens.com/cs/document/109476801/controlling-a-fan-(ebm-papst)-via-modbus-rtu-using-the-simatic-s7-1200?dti=0&lc=en-WW

sorry about that.

My q? 

I have vfd micno and I want to communicated with vfd .

modbus rtu rs 485

thanks for replay..

the recommended not clear 

because i I don't know what I write in master and slave .

PLC1200                           VFD MICNO

req.                                    ?

MB_ADDR                         ?

MODE                                ?

DATA_ADDR                        ?

DATA_LEN                          ?

DATA_PTR                           ?

SORRY FOR AGAIN ASK YOU..