i am making application on modbus.

[palpatel]

i am making application on modbus communication . i write data from modbus slave to application then increment that value by appliction but that value is not store in register so please help as soon as possible main problem is how to one element add in register of modbus

[mbrue101]

Hi, could you be more specific with what you are trying to do exactly?  Is the modbus a upper/lower or single byte style? is the data stored as mantissa/exp? also, i have had better luck using the modbus toolkit vs creating a ioServer.  and another also, sometimes the modbus registers are not zero indexed.  Sometimes they are one or 1/2 indexed. Depends on the device.  Here is a snippet of modBus code I had to write a while back.

[Daikataro]

First things first, we are missing a lot of information:

-What's your hardware? (it matters)

-What version of LV are you using? (might or might not matter)

-How are you connecting to your MODBUS device? For example serial or TPC/IP MB

-Have you read this? http://www.ni.com/example/29756/en/

Basically, what you want to do is a simple MODBUS Read/Write, which can easily be accomplished by the VIs in the link I just posted. Refer to your instrument's user manual to know the exact registries you want to read and modify, and make sure you can do so, since some registries are read-only. The algorythm for MODBUS is as follows:

Define what registry (or registries, some are 64 bit and handled as 2x 32 bit registries) you want to read or write, format your data in the correct type (some are 32 bit signed, some unsigned) and execute operation.