Siemens S7-300 I/O addressing question

andyhart21

Member
Join Date
Dec 2017
Location
Chesterfield
Posts
3
Good afternoon, I am hoping someone out there can help me with a query I have about Siemens S7-300 I/O addressing.

We have an S7-400 PLC system with 17 x S7-300 remote I/O racks distributed around the plant. A need has arisen to add another 16 channels of DI to an existing I/O rack. If I do not have enough physical space (it is very tight) to add another 16ch DI at the end of the rack, my thoughts were to replace one of the existing 16ch DI's with a 32ch DI.
My question is, how will Step 7 allocate addresses to this 32ch DI? Will the first 16 channels be automatically addressed to the same as the old 16ch DI, and the second 16 channels be allocated new addresses? I hope this is the case as the existing code obviously uses the original 16 channels.

Also, what is the limit for adding I/O to a rack? Is it just a case of connecting a new module (if this is the way I go) with a bus connector and configuring it in the hardware configurator? I have never changed a module for a different type or added new I/O before so this is new ground for me, I have only ever changed like-for-like. The configuration on this rack at present is as follows:

PS307 PSU
SIMATIC ET200M / LINK
SIMATIC ET200M / LINK
SM321 16ch DI
SM322 16ch DO
SM322 16ch DO
SM331 8ch AI 4-20mA HART

Thanks in advance

Andy
 
You can set the address to what you want but I'm pretty sure it has to be consecutive addresses within the module. In other words, you won't get the same address as the original module.

If you want to check it out, just open the project offline and then go to hardware configuration and remove the old and insert the new one and you'll see what options you'll be presented with.
 
Thanks for the reply. Sounds like an additional 16ch DI module is the way I should go if possible then. The problem is I cannot do any live testing on the system as it is always in use and I do not have any spare hardware to play with. This is having to be planned in 6+ months ahead to coincide with an outage period at the plant, and will have to go through a rigorous management of change procedure, so I am just trying to get as much information as possible beforehand.

Cheers
 
It all depends on the addresses set for the other digital inputs modules. If there is a gap in the addressing then a 32 input card could have the same base address.

gaps.jpg
 
I think your best course of action would be to find an appropriate trash recepticale, and place the S7 in there and go Allen Bradley :p. I gotta start diversifying and looking into these guys more.
 
It should not be a problem to replace this module. There should not be any problem in using the same addresses and adding 16 more addresses. Just be aware you have an up to date copy of the code. I would take an upload before making any changes. The plc has to go into stop when you download another hardware config to the plc. You can replace an older hardware with a newer hardware but not the other way around without a hardware change and download.
 
You have a PS307 PSU as the 1st module in the rack.
You can save one slot by moving this module to another position. It does not have to sit in the same rack as the other S7-300 modules.
In this way you dont have to add a 32-channel module and change wires or make program changes to the existing parts of the program.
 
What is the "SIMATIC ET200M / LINK" ?
And why are there 2 per rack ?

Are they really IM Send-receive expansion modules for S7-300 racks ?
Or are they IM modules for profibus or profinet ?
If so, why are there 2, since there can only be 1 per "normal" profibus/profinet rack ?
Or is that actually a hardware-redundant rack with the special backplane modules which supports 2 IMs per rack ? The i/o does not look like a redundant setup.

Too many questions !!
Post an exact list of type numbers and/or photos please.
 
Thanks for all the replies guys.

The Simatic Link modules are the IM153 Profibus DP interface modules, and yes there are two for redundancy. I have attached a picture of the system architecture which shows the interface between the CPU's (again redundant) and the remote distributed I/O racks. Note that the remote I/O rack shown in this drawing is not the one in question above.

Architecture Edit.jpg
 

Similar Topics

Hi, How to define Siemens(S7-300 via MPI) plc tags in weintek HMI Mt8102? I know Communication is established but i am not defining addresses...
Replies
1
Views
1,692
Hi, How to define Siemens(S7-300 via MPI) plc tags in weintek HMI Mt8102? Communication is established but i am not defining addresses correctly...
Replies
0
Views
1,036
I have spent a couple of weeks now hunting around for information to step7 indirect addressing. There are many, many discussions relating to this...
Replies
5
Views
10,325
Hello, I need to be able to write time directly to a Siemens TON SFB4 timer. How can I do that through Wonderware Intouch using DasSiDirect...
Replies
2
Views
4,722
Hello. I'm new here and new the Siemens CPUs. The CPU has no documentation and I'm a little lost on the Siemens website. I understand how...
Replies
13
Views
13,257
Back
Top Bottom