hello people

I have a very interesting problem with my modbus communication between these two PLCs.

the 1215C is MASTER and Fatek is slave.

The function in 1215C reads 10 Words from Fatek.

there is a pointer to M530.0 to put the data into when it reads it.

when I change the word in my slave two words on the master change and I dont know why.

i dont understand the problem.

why is there a change in a 32bit length area of memory?

the project is running fine. but I am just wondering why I have this problem?

is there a problem with my function or the protocol from Fatek side has a problem.

thank You for the Response

the pics from my functions are attached.

unknown user

just one big thing, some missunderstandings! Look to your video, you set some values but you have there 17 Bit value not 16 (1 WORD)

 

in the slave i dont have control over a 17bit of memory the way i assign the values.

unknown user

Hope I good see that in video. Next question is that WORD addresses start with even numbers - MW530, MW532, ... f.ex.  and you have there also MW531 which is wrong, you simply overview your WORDs. This can be problem.

this is my problem actually!

my problem is that when i change a 16 bit word in slave in my master 32 bit of memory Changes.

I monitor MW531 because when i change MW530 the MW531 Changes.

thank u Kaulquappe and Duris_I

you are right.

the problem was in my addressing of the memory in 1215C and the Function is doing its job perfectly!!! so everything is ok right now.

thank you guys

Hello Again

I have a new Q.

how does the memory in S7 work?

if I change M0.1 after the word MW0 arrives at the slave my destination shows that the high Byte of that word changed.

for example I do this:

0000_0000_0000_0001

after the word goes through the network it arrives like this:

0000_0001_0000_0000

again I know that a byte swap would solve the problem and i dont have any bugs in my program because of this. I just dont understand the reason?

so the 16th bit of MW0 is MB0.7?

How is this Logical? Im Not saying its not I just cant see it!