Siemens S7 Addressing

antjon1

Member
Join Date
Feb 2006
Location
Tennessee
Posts
29
Hey, I am in the process of learning how to program the S7 PLC, and I am trying to make sure that I understand how the Siemens addressing works. I am very familiar with AB's addressing, but Siemens is pretty different from that. From what I understand, each card, regardless of how many terminals, has 4 bytes of memory assigned to it. So if there are 4 cards, the 1st and 3rd are input, and the 2nd and 4th output, the addressing would be like this:

I0.0-i0.7, I1.0,
Q4.0, Q5.0
I8.0, I9.0
Q12.0, Q13.0

(All cards are 16 bit)

Please let me know if I am understanding this correctly.

Thanks!
 
If you have been a little inaccurate and in essence ment to state this
So if there are 4 cards, the 1st and 3rd are input, and the 2nd and 4th output, the addressing would be like this:

I0.0-I0.7, I1.0-I1.7,
Q4.0-Q4.7, Q5.0-Q5.7
I8.0-Q8.7, I9.0-Q9.7
Q12.0-Q12.7, Q13.0-Q13.7

(All cards are 16 bit)
then you do understand this correctly.

Kind regards,
 
OK good. Its definitely different from AB. I left off the parts you added in, i ntended them to be there, though, since I am kinda tired right now.

Thank You very much for your help!!!!
 
Hey Antjon,


You're right about the system default settings. They reserve 4 adressing bytes per digital IO module. However you can override these settings and enter a specific start adress. You can even give the same adresses to both DI's and DO's, so you would get a config like this:

module 1: I0.0-I0.7, I1.0-I1.7,
module 1: Q0.0-Q0.7, Q1.0-Q1.7,
module 1: I2.0-I2.7, I3.0-I3.7,
module 1: Q2.0-Q2.7, Q3.0-Q3.7

On the other hand, when replacing 16DI/DO modules on such a system by 32DI/DO's, the hardware configurator will search for the first 4 available, consecutive addressing bytes:

module 1: I0.0-I0.7, I1.0-I1.7,
module 2: Q4.0-Q4.7, Q5.0-Q5.7, Q6.0-Q6.7, Q7.0-Q7.7, <= 16DO replaced by 32DO
module 1: I2.0-I2.7, I3.0-I3.7,
module 1: Q2.0-Q2.7, Q3.0-Q3.7

(just thought you should know...)
 

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