communication using modbus protocol

hi to all automation techies,
i am using allen bradley micrologix 1500 lrp series. i want to

interface my plc with dcs which supports modbus protocol.

please suggest suitable way for interfacing both hardware & software

regards
jose

jose. Welocme to plcs.net Please feel feel register if you want to get into the loop here.

The MicroLogix 1500 has a very good Modbus implementation and can act as either a RTU Master or RTU Slave. In the MicroLogix the main thing is to select under "Channel Configuration" either Channel 0 or 1 and then under "Driver" pulldown list choose "Modbus RTU Master/Slave". I would guess that the DCS you have will be the Master, so it is likely the Micro1500 will be the slave. If this is the case you will need to map some Micro1500 datatables to act as the Coils (0XXXX), Contacts (1XXXX), Inputs Registers (3XXXX) and Holding Registers (4XXXX).

The hardware is a RS232 simple serial connection.

Lacking any more information about your system it is hard to give more detail, but the above is the general idea. It should be pretty simple really.

thanks

sir
thank u for ur quick and prompt reply, i really appreceiate.
we are in the field of burners and its complete automation
since most of our projects(plc) are in stand alone application ,we never had to interface with dcs
but since we are integerating plc with dcs for first time i have few more queries
as u mentioned to map database to act as coil, contacts i/p registers
hold registers ,how it is done please help me sir

i have already registered with this site

regards

jose

In the MicroLogix the main thing is to select under "Channel Configuration" either Channel 0 or 1 and then under "Driver" pulldown list choose "Modbus RTU Master/Slave".

Click to expand...

thanks

sir
thank u for ur quick and prompt reply, i really appreceiate.
we are in the field of burners and its complete automation
since most of our projects(plc) are in stand alone application ,we never had to interface with dcs
but since we are integerating plc with dcs for first time i have few more queries
as u mentioned to map database to act as coil, contacts i/p registers
hold registers ,how it is done please help me sir

i have already registered with this site

regards

jose

and if iam using cpu 226

sir

this portal is really helpful for newcomers like me i am really

impressed by ur suggestion and tips.

i have one more doubt ,if i am using siemens s7 cpu type 226

with touch panel 270 -10' which is in our scope , which will be

integerated with dcs using mod bus protocol (provided by client)

what will be solution

regards jose

The 1500 has two comm ports. I usually use one port tied directly to the touchscreen, and one for communications links. You don't need to use the same protocol on both.

The problem is that Modbus RTU can only have one "master" initiating the data requests. Both the SCADA system and most touchscreens want to act as masters, so they can't share the same port.