Skip to Content

Register Login

Industry Online Support

Technical Forum

Navigation

communication between s7-300 and 9 honeywell controllers

Created by: patel at: 7/7/2009 9:43 AM (4 Replies)

Rating (0)

Thanks 0

5 Entries

7/7/2009 9:43 AM	Rate (0)
patel Posts: 134 Rating: (2)	hi..all.. i m doing one project of MODBUS communication between S7-300 and HONEYWELL controllers.. I have successfully established commu. between 1 controller and s7-300..it is working fine... Now, i want to know how i can communicate with multiple slaves using one CP341..because i have 9 controllers to communicate... SO,what changes i need to do in hardware wiring and also in software to do this...HOw can i make program for this? please send me if u have any sample program for this.. its urgent pls..
patel Posts: 134 Rating: (2)
Suggestion To thank Quote Answer

7/7/2009 11:04 AM	Rate (0)
dchartier Grandmaster-Expert Joined: 9/27/2006 Last visit: 12/7/2024 Posts: 12301 Rating: (2692)	Hello patel; Basically, once comms have been established between the master and a single slave, you have to repeat the operations for each individual slave you want to access, with new Send_DBs and Recieve_DBs for each. And you have to schedule the calls of each so they do not overlap. Have a look at the sample project provided by another user, DR75, in the following thread: /tf/WW/en/Posts/16268 You might find it instructive. Hope this helps, Daniel Chartier

Suggestion To thank Quote Answer

7/7/2009 9:31 PM	Rate (0)
jklm Platinum Member Joined: 12/22/2006 Last visit: 1/25/2022 Posts: 1742 Rating: (309)	Hello, be sure to run RS485 and not RS232.
	Best regards jklm Suggestion was helpful? Feel free to rate it.
Suggestion To thank Quote Answer

7/9/2009 8:19 AM	Rate (0)
patel Posts: 134 Rating: (2)	Thanx a lot sir... this example is realy realy helpful to me... i have one more querry..please sort it out.. Now, i want to read and write both to my controllers. So, i need to use function code 3 and 6 both right? but my doubt is that, if i m reading data from controller using fun.code 3 currently,then at the same time can i write data to same controller using fun.code 6... Do i need to use FB8"P_SND_RK" twice?means once for reading and once for writing? OR it is to be done with one FB8. and HOW it can be done?why i have doubt is because, LENGTH will be different for reading data and writing data...so, i am confused.. please if u have any sample program for that..
patel Posts: 134 Rating: (2)
Suggestion To thank Quote Answer

7/9/2009 9:24 AM	Rate (0)
fritz Diamond Expert Joined: 10/7/2005 Last visit: 12/8/2024 Posts: 3028 Rating: (1057)	patel Now, i want to read and write both to my controllers. So, i need to use function code 3 and 6 both right? That is in principle correct. Have a look at Modbus Function code 16 too, which allows writing of multiple registers (Modbus function code 6 allows writing of only ONE register). patel but my doubt is that, if i m reading data from controller using fun.code 3 currently,then at the same time can i write data to same controller using fun.code 6... No you can NOT (one request at time, have a look at thisthread for some technical background info about this) patel Do i need to use FB8"P_SND_RK" twice?means once for reading and once for writing? OR it is to be done with one FB8. and HOW it can be done?why i have doubt is because, LENGTH will be different for reading data and writing data...so, i am confused.. You'll always need a P_SND_RK/P_RCV_RK pair for any Modbus READ function code. A Modbus WRITE function code can hoever be done with only P_SND_RK (no need for P_RCV_RK, but it doesn't "hurt" to keepit'scall active anyhow when doing a Modbus Write function code). Yes, length will be different and needs to declared in the so called "Modbus header" of yourrequest DB. I'm afraid you will have to study the Modbus Master manual (have a look at the manual folder in your Simatic program group where it should be if you installed the software, alterantivelyyou can download it here) I hope this helps
	Last edited by: fritz at: 7/9/2009 9:27 AM need to learn how to spell corrrrectly.... Cheers fritz The advice and opinion given in this thread is that of the author and does not necessarily reflect the views of I S Systems Pty Limited. To find out how I S Systems can help you with your automation needs please visit www.issystems.com.au.
Suggestion To thank Quote Answer

|

Share this page:

Share this page on...

Follow us on