S7 over tcp bit manipulation

[Ido Tamir]

Does anyone know how to set a single bit using the WRITE \ FETCH mechanism?
I am using VB6 and connected via TCP to an S7 PLC.

Currently I'm using a whole byte to do this, but that means I need
a byte for every bit I'm setting ..

Any other way to do it?

Thanks

Ido

 

[ArikBY]

Shalom Ido Welcome to this froum.

Sorry I can not help you with Siemens.Siemens is not my expertise.

Good Luck

 

[DesertDog]

If you organize your communication data correctly you can manipulate 8 bits separately as needed and move them into a byte that is sent. On the other end they can be broken out similarly. This allows you to control the bits singly but send in byte or word format which is more efficient anyway.

 

[adina]

Hi Ido!

I had the same problem trying to connect Cimplicity HMI to S7-300,
using Cimplicity OPC server for Siemens TCP/IP. All the
boolean variables are read-only when using this OPC Server.
So I had to use a whole byte for each push button I had in my
program!

A way to go around this issue, especially if you have to optimize
the memory usage, would be to "pack" more bits into one byte
and write all of them at the same time. I had started doing something
like that, but I had to give up, and provide just a working
solution, not an elegant one, in the shortest amount of time.

Regards,
Adina