adccommunitymod (AutomationDirect) asked a question.
Created Date: June 27,2005
Created By: pelacables
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Hi folks, I have a conceptual question and reading the manual did not sovle it at all.Let me explain my configuration and the my question: One DL-06 "beeing " the master (station number 1), and ten DL-05 "being " the slaves (stations number 2 to 11). I have conected all via RS-485 (with FAISOCN converters). At this moment, DL-06 is the one who reads/writes over all 05's using Mrx/wx. But is there any way to have multiple comunications in same line? I mean, DL-05's writing over DL-06, and 06 to 05? Manual says that only master is able to write/read over slaves...but as 05's have RX and RW functions.... Cheers! Arnau
Created Date: June 27,2005
Created by: bcarlton
It's not a problem of CAN the 05's initiate conversations. It's 'collisions '. There is nothing built in to Modbus or Directnet to prevent simultaneous transmissions which would clobber each other.
Ethernet has automatic detection of the line being busy (Carrier Detection) and of self correction if simultaneous conversations do start (Collision Detection).
If you need this 'peer to peer ' type communication go with ECOM modules (if you have the free slots).
Created Date: June 29,2005
Created by: AlvinBennett
I 've never used multiple 05's as masters but i have used multiple 06's and used control bits passed between the masters to keep from message collisions and it's been working fine for over a year.
Created Date: June 29,2005
Created by: bcarlton
So you have provided a control at the application level that which does not exist naturally in the lower level of the protocol. Excellent.
Created Date: June 29,2005
Created by: marksji
Now that is slick!
Created Date: June 30,2005
Created by: PCallaghan
What a great idea.
Created Date: June 30,2005
Created by: pelacables
Yes this is possible, but as bcarlton says, you must controlthe colisions. In my case, I cannot ensure when a 05 will do a comunication, so I cannot control the line...
Many thanks for the idea,
Cheers!
Created Date: June 30,2005
Created by: clasentech
Yes this is possible, but as bcarlton says, you must controlthe colisions. In my case, I cannot ensure when a 05 will do a comunication, so I cannot control the line...
If you constantly and sequentially "give " each PLC it's "permit comm " bit then you can do this. Its easier to have the sequence start over with what ever PLC received actual data (and the comm bit)
A says B has the ball. B says C has the ball. **E wants to send critical data to B.** C says D has the ball. D says E has the ball. E sends data and the ball to B. B says D has the ball.
Of course you could make it more intense then this if you need to.
Did that make sense?
Created Date: June 30,2005
Created by: franji1
http://forum1.automationdirect.com/board/cool.gif Cool! A Token Passing network implemented in Relay Ladder Logic - hooda thunk it!?!
Created Date: June 27,2005
Created by: pelacables
Hi folks,
I have a conceptual question and reading the manual did not sovle it at all.Let me explain my configuration and the my question:
One DL-06 "beeing " the master (station number 1), and ten DL-05 "being " the slaves (stations number 2 to 11). I have conected all via RS-485 (with FAISOCN converters). At this moment, DL-06 is the one who reads/writes over all 05's using Mrx/wx. But is there any way to have multiple comunications in same line? I mean, DL-05's writing over DL-06, and 06 to 05?
Manual says that only master is able to write/read over slaves...but as 05's have RX and RW functions....
Cheers!
Arnau