Modbus ASCII applications and its difference with Modbus RTU

Greetings nicest people on earth,

I am reading about Modbus Protocol. Through internet reading, i got to know about the types of Modbus.
Now my question are:

1: Where is Modbus ASCII used (its applications nowadays)?
2: Can i recognize a Modbus ASCII?

I know that if i see a PLC communicating using a Serial Cable with the DB-9 Connector, then i can guess that it is Modbus. But, whether it is Modbus RTU or Modbus ASCII is still not clear to me. In this regards, can you please explain the following:

1: Does Modbus ASCII also use the Rs-232, RS-422 and RS-485 Protocols?
2: Is there any difference in the Electrical Voltage levels of Modbus RTU and Modbus ASCII?
3: What is the main factor that will make one choose Modbus ASCII over Modbus RTU?

Anxiously waiting for answers from the brilliant minds out there
Regards,

Hi,

did you read: https://en.wikipedia.org/wiki/Modbus

Doesn´t it answer (some of) your questions?

Klaus

Greetings KlausST

Yes, i have read this link too. And not really, this link does not talk much about the queries that i have stated above. My queries have risen basically because i have not practically seen a cable in my hand and say,"Hmm... so, this is the ASCII Cable"

Regards,

Hi,

you talk about and mix different things.

Protocol:
* MODBUS ASCII
* MODBUS RTU

Electrical interface:
* RS-232
* RS-485
* RS-422

Generally you can use any interface with any protocol.

It´s like:
* Protocol --> language (English, German ...)
* Electrical interface --> transport medium (Letter, wired telephone, radio)
-->You may send informations in English as well as in German language via letter, telephone or radio...

*****

--> There is no "ASCII cable"
(As there is no telephone line for English and another telephone line for German)

*****

I know that if i see a PLC communicating using a Serial Cable with the DB-9 Connector, then i can guess that it is Modbus.

Click to expand...

It could also be:
* PROFIBUS
* MPI
*....

Klaus

Added:
Read this for more detailed informations: www.modbus.org/docs/Modbus_over_serial_line_V1.pdf