Modbus communication for ML1100 and Honeywell dcs

chandu_bagal · May 22, 2010

I am using Micrologix1100 as Modbus slave and
Honeywell dcs as Modbus mater.

ML1100 communication parameters configured with the Channel0 are as below
Driver- Modbus RTU
Node Adress-01
Baud-9600
Parity-NONE
Stop Bits-1
Modbus Data Table File Nos.
coils-9, Input registers-21
contacts-0,Holding Registers-20
protocol control- No Handshaking, Inter Char. Timeout-0
Pretransmit delay-1000 ms
On Micrologix1100 side we have 1763-NC 01 cable.
same parametrs i am configuring on dcs side.
On DCS side we have rs-485 port.
Communication is not established.

Please somebody can help me.

Thank you!
Chandrakant

Mickey · May 22, 2010

Are the node addresses different?

Also with RS485 comm, one of the first things to try is swap terminals "A" & "B".

chandu_bagal · May 22, 2010

Mickey said:
Are the node addresses different?

Also with RS485 comm, one of the first things to try is swap terminals "A" & "B".

I am using single node as MicroligX1100 as slave with node adress-01.
Also I have tried by swapping A & B terminals. Terminal connections are as below
ML1100 Honeywell DCS
A ---------------------------------------RX+/TX+
B----------------------------------------RX-/TX-

But still didn't establish communication.

Please suggest.

Thanks

Chandrakant Bagal

Eddie Willers · May 22, 2010

In Modbus RTU protocol, the Master does not have an address. It's just "the Master".

You need to change at least two things on the MicroLogix 1100 controller.

Configure the Handshaking setting as "No Handshaking (485 Network)". This enables the RS485 pins on the MicroLogix.

"2-wire" RS485 requires THREE (3) wires; A, B, and Common. If the Honeywell system does not have a dedicated Common wire, connect the Common pin on the 1763-NC01 to the Honeywell shield or ground.

Mickey · May 22, 2010

Sorry about the Master addresses advice.

Here is a AB knowledgebase article about the "No Handshaking ( 485 Network)"
as stated by Eddie Willers above.

http://rockwellautomation.custhelp.com/app/answers/detail/a_id/65658

danw · May 23, 2010

Mickey, your link requires registration as a Rockwell support customer, so I can't get in.

Your answer intrigues me though, because on a different forum, the Modbus master on a Honeywell DCS was given a node number.

Is that article small enough to post here?

Dan

Mickey · May 23, 2010

danw said:
Mickey, your link requires registration as a Rockwell support customer, so I can't get in.

Your answer intrigues me though, because on a different forum, the Modbus master on a Honeywell DCS was given a node number.

Is that article small enough to post here?

Dan

The access level is "Everyone" so just register. Its free.

It does not say anything about master/slave addresses.

I have seen PLC's with their serial ports configured for Modbus RTU and the port can be used for master or slave. There was no setting to configure
the ports for either one. But you had to give it an address.

See txt below for what it says.

danw · May 23, 2010

Thanks for the heads up. When I saw the TechConnect Support Contract field, I gave up, but it takes a registration without a support contract entry.

Dan

Mickey · May 23, 2010

danw said:
Thanks for the heads up. When I saw the TechConnect Support Contract field, I gave up, but it takes a registration without a support contract entry.

Dan

There are not that many "everyone " articles. And even those are disappearing fast.

chandu_bagal · May 24, 2010

Mickey said:
There are not that many "everyone " articles. And even those are disappearing fast.

Thank you very much Eddie,Micky for helping on this.
I could establish communication successfully by configuring Contol line - Non Hand shaking (485 Network)

Thanks once again!

Chandrakant Bagal

Modbus communication for ML1100 and Honeywell dcs

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