How to read PLC memory with dotnet

[paul56]

Hi,

I need to read (or write to)the memory contents of an Allen Bradley PLC. In PLC programming addresses are typically like N7:0, N7:11, or B3:200/0, B3:200/11, etc., etc. How many bits does each such address contain? Can the same address formats be used to read from or write to them using the modbus protocol (TCPIP). The programming language being used is VC#.net. Is there any difference for coils and registers?

I'd very much appreciate a clear answer ASAP. Thanks in advance.
Regds

 

[nettogrisen]

First of all. N7:0 and N7:11 are integers. B3:200/0 and B3:200/11 are bits. I suggest you read the manual on the PLC. We still don't know what PLC you have. If its a micrologix 1400 rev. B it supports modbus tcp. I don't know if any SLC does. Do a forum search on "advanced HMI". It's a VB.net project that supports ethernet/IP communication with logix500 controlers written by Archie, a member of this forum.

 

[paul56]

how to read PLC locations with DOTNET

Hi Jesper,
The PLC is Allen Bradley 1766-L32BXB. While it is nice to know that the Ns are integers and the Bs are Bits, I would appreciate info on how to address these locations for the purpose of reading/writing, similar to how one addresses microcontroller memory. The spec sheet seemed to indicate that the analog input is 12bit unsigned. I shall check on the advanced HMI suggested. However, if anyone could offer some more info I'd be thankful.

Regds

 

[harryting]

So you are attempting to write a driver to communicate to the PLC? Why not just get an off the shelf product?

 

[bernie_carlton]

here are links to the User Manual and Reference Manual for this series

 

[nettogrisen]

Ok, so your PLC is a Micrologix 1400, if it's rev. A it doesn't support Modbus TCP, and you will have to find a nother method of getting your data (Modbus RTU, Ethernet/IP). If it's rev. B it supports Modbus TCP. You will have to map the memory addresses (N7:0, B3:0/0 etc.) to modbus adresses using Logix500 programming software.

 

[paul56]

Hi all,
Harryting:Basically its a question of cost and the thrill of trying to write as much of your own code as possible.
Bernie: Thanks for the links.
Jesper: Shall try to do as suggested. I was hoping that some example mapping of N, I, B or O addresses into the appropriate form would be given, so that I could take over from there.
e.g.: N7:0 maps to .....
B3;200/5 maps to ....
The mapped expressions would be directly usable in dotnet code to access the PLC memory locations.

Thanks a lot.

 

[dmroeder]

AdvancedHMI is the way to go if you can use VB.NET

Click

 

[nettogrisen]

Hi all,
Harryting:Basically its a question of cost and the thrill of trying to write as much of your own code as possible.
Bernie: Thanks for the links.
Jesper: Shall try to do as suggested. I was hoping that some example mapping of N, I, B or O addresses into the appropriate form would be given, so that I could take over from there.
e.g.: N7:0 maps to .....
B3;200/5 maps to ....
The mapped expressions would be directly usable in dotnet code to access the PLC memory locations.

Thanks a lot.

The thing is that YOU have to do the mapping using Logix500. They are not pre-mapped. Basicly you could write your .net application as you see fit and then just map the adresses afterwards.

 

[paul56]

DMRoeder: Advanced HMI seems great. But,how do I use the controls/dlls with C#. I would like to use the Advanced HMI together along with the other adminstrative features, etc., already in my code. Can anyone provide info or suggest useful URLs? Thanks in advance.