Modbus Communication

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Hi Everybody
I am working on Modbus for First time.
my question regarding modbus is
In Modbus Communication we receive data in integer.how can we get the orginal data.
 
Are you reading an integer but trying to get the discrete status bits it represents? In that case you have to "bit strip" the data - essentially look at each bit in the word of data and map it to a bit type variable. The mechanics of this vary with the receiving device and software. More details will be helpful.
 
THANKS TOM

BUT I WANT TO KNOW THAT IF I AM JUST READING DATA AND I DONT WANT TO GET DISCRETE STATUS BIT THEN HOW CAN WE GET THE ORIGINAL DATA.
ALSO SEND THE SOME MORE DETAILS ON BIT STRIPING AND ITS OPERATION.
MY PERSONNEL MAIL ID IS [email protected] or [email protected]

I AM WAITING FOR YOUR REPLY
DO SEND ME THE ANSWER TO MY QUERY
OTHERS ARE ALSO WELCOMED TO SEND ME ANSWER TO MY QUERIES ON MY MAIL ID MENTIONED ABOVE.
 
First, I don't send responses by Private Message - I like to keep things on the forum so all can benefit and anyone can correct my errors.

Second, there isn't enough information in your post for any more than a general answer. The mechanics of bit stripping depend entirely on the sending and receiving devices. PLCs can store the bits in different order (big endian vs. little endian"). The receiving device will have a specific command structure and syntax for decoding the bits as well.

Provide more details, and you will get a better answer.

Remember, there is a huge variety of devices that use Modbus protocol!
 
Modbus is limited to 16 bit integers. You have not explained what you mean by "Original data" ?
I have experienced certain amount of frustration with Modbus comms myself. Trying to write/read data to/from GE Fanuc's Quick PanelView which only works with 32 bit Integers and LREAL's.
It took me several days to hash out VB script routines to properly read and write whole range of negative and positive numbers.
I had ended up calculating 2's complement to convert negative numbers to a proper format.
 
Ans

Umesh,
if you need to monitor Interger data use Holding register
Lets take example of some counter value you can put it in 40100 and transmit or recive it
if you wnat to read stuus analog data you need status register
30002 etc.

Bye
sandeep
 

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