SiePortal

The integrated platform for your product selection, buying and support workflow - bringing together Industry Mall and Online Support.

Products & Services
- Menu temporary not available
- Menue temporary not available
- {{item.title}}
Support Support
{{(apiData.Support | filter:{'rank':1}:true)[0].title}} Support
- Menu temporary not available
- Menue temporary not available
- {{item.title}}
MySiePortal MySiePortal
{{(apiData.MySiePortal | filter:{'rank':1}:true)[0].title}} MySiePortal
- Menu temporary not available
- Menue temporary not available
- {{item.title}}
Cart ({{apiData.CartCount}})

Navigation

Modbus Master communication

8/5/2010 1:09 PM	Rate (0)
rick209 Posts: 33 Rating: (0)	Dear All I am working on a project where i have cp 341,there are two xcell controllers which will act as modbus salve,in these two controllers, data from 64 feeders or motors comes through motor vision relays.Now my problem is that how i will configure two slaves ,i have to read status bit and also write bits in order to start and stop the feeders,where i will get the status bit and where i have to write the control bits.will i have to give different addresses for both the slaves or only one add as both the controllers are communicationg with each other through backplane bus. Looking forward for your reply. Thanx& Regards
rick209 Posts: 33 Rating: (0)
Suggestion To thank Quote Answer

8/5/2010 5:18 PM	Rate (0)
J_Bell Posts: 5822 Rating: (412)	Hello rick, I am sorry, I am not as deep into MODBUS RTU as I would like to but maybe this Thread will already help you: /tf/WW/en/Posts/46567#top Best regards J_Bell
J_Bell Posts: 5822 Rating: (412)
Suggestion To thank Quote Answer

8/9/2010 1:29 PM	Rate (0)
rick209 Posts: 33 Rating: (0)	Thanks a lot but in my case i will have to read and write bits and analog signals too,so how many jobs i have to make and what will be the function code for all the jobs.
rick209 Posts: 33 Rating: (0)
Suggestion To thank Quote Answer

8/9/2010 2:02 PM	Rate (0)
smiffy Platinum Expert Joined: 1/17/2007 Last visit: 4/15/2025 Posts: 1560 Rating: (540)	The function codes you will need to use are:- Function code 16 - Write Multiple Holding Registers. This is primarily used for writing one or more analogue values. But it could just as easily be used to writing digital signals if they are packed into register as 16-bits. However, the latter would need additional logic at the slave end to manipulate out the individual bits from the 16-bit register. Function code 15 - Write Multiple Coils. This writes one or more boolean signals. No need for extra logic in the slave for this one as the modbus protocol handles the bit manipulation for you. There are 2 others that you might want to use. Function code 6 - Write Single Holding Register. Similar to FC16 but only writes 1 holding register. Kind of superfluous as you can use FC16 to write 1 register as well. Function code 5 - Write Single Coil. Similar to FC15 but only writes 1 coil. Kind of superfluous as you can use FC15 to write 1 coil as well.
	Programming today is the race between software engineers building bigger and better idiot proof programs, and the universe producing bigger and better idiots. So far, the universe is winning...
Suggestion To thank Quote Answer
This contribution was helpful to 1 thankful Users J_Bell

8/10/2010 5:50 AM	Rate (0)
rick209 Posts: 33 Rating: (0)	Thanx sir for ur valuable information
rick209 Posts: 33 Rating: (0)
Suggestion To thank Quote Answer

Share this page:

Share this page on...