S7-300 Addressing...I am new to Siemens

SNK

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Join Date
May 2004
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I am an Allen Bradley programmer, and have recently been asked to work with some of the Siemens S7 stuff for work.

My question is simple. Is the addressing for PI devices the same as I would expect on a S7-300 rack as an allen bradley SLC or Contrologix system? Maybe this will make my question easier to understand.

Slot 0 Power Supply
Slot 1 CPU S7-300
Slot 2 Profibus/MPI
Slot 3 MI module
Slot 4 Digital Input module
Slot 5 Digital Output Module

Basically, how do I address the first digital INPUT module in the program? Is the first byte of I0.0 and the second I1.0?
And the Output in card slot 5 Q0.0 and Q1.0?

In AB world, we reference with the card slot... eg I:4.0/0 and O:5.0/0

Furthermore, is there any set pattern that the I/O cards have to be set up on the local rack???
In my first attempt today to program, I cannot get the I/O cards to work properly online.

I have downloaded the S7-300 manual, but it does not go into detail about the specifics of rack location and addressing.

Thanks for any insight people.
 
kcarlen

Welcome to the wonderful world of Siemens PLCs.

When you set up your PLC rack in the hardware configuration, the software gives the I/O modules default addresses, have another look at the hardware setup and this will tell you the address that you are looking for.

The I/O does indeed go in bytes e.g I0.0 .. I0.7 then I1.0 .. I1.7 and so on, outputs are addressed the same, but using Q. There is no set pattern that the I/O cards have to be set up in the rack, but if you attempt to put a 'card' in a wrong location the software will tell you.

Is this the manual that you are using? This manual is the instruction list set for the S7300 range.

Paul
 
Thanks Paul.
The manual that you have linked me to is not the same as the s7-300 setup manual that I received. I am at home now, and I don't have a copy of the download in front of me.
I am still not 100% clear on the addressing scheme.

Say I have 10 Digital Input cards in the rack, after the 3rd imaginary (MI)slot. The first used slot is No. 4, then 5 then 6 ......
until 14 is reached...correct?

What is the easiest way to locate the I/O on card 8 for example? Do I have to go to the cards, count up to bytes until I get to the card that I want?
It makes NO SENSE to me, considering the AB cards can be referenced to the CARD SLOT. From what I am seeing here, it is NOT the case.

Is it safe to say that I can put 3 DI cards in the 4th,5th and 6th slot, and then put in 3 DO cards in the 7th, 8th and 9th slots?
Could you indicate what the address would be for card 9, output 5 of the first byte?

Thanks a million for your help Paul.
 
Sorry to butt in

Hey Kcarlen.. sorry to butt in, but you and I are sort of in the same boat. You from a programmers point of view and me from a troubleshooters point of view. This Step7 stuff is way wierd when you are used to RS logix aint it? Any way I just wanted to tell PLucas thanks too. Cause that link to the addressing PDF file came in pretty handy.... Thanks and sorry for butting in ToddM.
 
Come on guys- the basic manuals and "getting started" manuals are installed when Step7 is installed. They are under Start> Simatic> Documentation>
Your making it too hard. Also- ask your distributor for the Step 7 - Step by Step CD. For you lazy guys that dont read- you can clink through the movie files.
 
Hello Guys,

In S7-300 you have two methods of addressing:the fixed slot addressing,this applies to the CPU's with lower number, e.g CPU 314.

Variable slot addressing, you will get it when the CPU number goes up, e.g CPU 315-2DP, here you are free to address your I/O's the way u like.(you can obtain it by not checking SYSTEM SELECTION in the ADDRESSING TAB)

In fixed slot addressing Slot 4 occupies bytes 0..3 , Slot 5 occupies bytes 4..7 & so forth (This is to support the 32 bit I/O's modules).

In variable slot addressing(higher number CPU's), you could choose to accept the defaualt of the fixed slot addressing , or you might need to put your own address (this is done by un checking the SYSTEM SELECTION in the ADDRESSING tab).

Just try it, you will find it very easy to follow.

N.B

S7-300 slots number begins from 1 & goes all through to 11 , & hence that the S7-300 power supply is not an intelligent card(that means you could use any power supply rather than Siemens to supply your PLC system), for all that slot 1 could be left empty in your hardware configuration.

Regards
hagos
 
hagos - feature of changing default address of card doesn't depend on CPU number but on its firmware version (e.g. it works even on newer CPUs 312).
Deafult slot addresing you described is OK for digital IO modules. For analogue modules default addresses start from byte 256 in slot 4 and are incremented by 8 words.
On-board IO (like CPU314C IOs) are treated a little bit differently.
The best source for those information are manuals supplied with Step7. In this case: "S7-300, CPU 31xC and CPU 31x: Hardware and Installation".
BTW, have anyone ever read any of manuals ? Or you are too smart to bother yourself ?
 
Thanks guys. I have briefed the manuals, but nothing indicates that the cards can be placed anywhere, like my original question indicates.

I thank those that responded.

If anyone wishes to know anything about AB Controllogix, and you are overworked and underpaid....and sometimes don't have all day to read a manual....then feel free to ask me for information. I won't bite you for asking simple questions...

People are so quick to judge.
 
The freedom to place the cards anywhere is assumed by Siemens. I suppose they consider not being able to do that so fundamental it's not even considered. Let's face it, in an S7-400 the CPU can be placed anywhere - right in the middle of the rack if you want. Oooops, what am I saying? I should have said "...the CPUs can be placed anywhere..." Yup, stuff up to 4 CPUs anywhere you like in an S7-400 rack, squeeze the I/O anywhere in-between and let's rip! Now, that's flexible. And how do you address these I/O? Well, same way you do in a single CPU S7-300: I0.0, I0.1, I0.2 etc etc Couldn't be easier.

Ken.

PS : How come people always have the time and motivation to keep coming back to read a forum which just may have the single bit of information they want today, but never have the time or motivation to read the manual which probably will have all the info they need for the whole project? I've no problem with obscure or expert questions on a forum - these may not be covered adequately in standard mass-market manuals. But I have a slight sympathy with the manufacturers sometimes. We love to criticise them (esp. Siemens) but even when they make the effort to distribute comprehensive manuals with the product, we don't make use of them. And, no offence intended Paul, but how come you get thanked for a web-link? Did Todd also send a thanks to Siemens for the manual which "came in pretty handy". Or is it just nice to have a bot like Paul to do the searching for you?
Oh damn it, somebody keep that soapbox away from me - I've said too much already!
 
Ken

No offence taken.


originally posted by Ken M

How come people always have the time and motivation to keep coming back to read a forum which just may have the single bit of information they want today, but never have the time or motivation to read the manual which probably will have all the info they need for the whole project?

Point well made, but... to some people the manuals are not written in plain english, they are written by 'spring-heads' for 'spring-heads', us mere mortals, sometimes, have a problem grasping what the manual means.

I know this is a basic question regarding the addressing of cards, but even the simplest of problems stump all of us occasionally!

Most of the answers people receive here are written in a way that makes it easier to understand, they are written in a way that gets straight to the point, there's no need to trawl through pages upon pages of information just to find the sentence that you require.

IMHO forums should be a place to ask ANY question, be it a simple question or a more obscure/expert question, unless you're asking for your homework to be done! :D

Paul
 
Ken,

I know this is a basic question regarding the addressing of cards, but even the simplest of problems stump all of us occasionally!

Sometimes it is precisely the simplest problems that can hold you up longest - because the answers to them are usually not in the manuals!

I think Paul has pretty much said it, but one of the problems that I have as a relative newcomer to SPS systems (I've spent most of my 30+ years in Process Control on DCS systems and their predecessors) is that some problems involve things which the author of the manuals either considered trivial, or more likely, didn't consider at all because it was completely intuitive to him.

I'm one of those rare people who always reads the manual first, (finding them on the Siemens website can be difficult sometimes though :p ), but it doesn't always help. I think a part of the problem is that in many cases nowadays the manuals are no longer written by technical authors, who are trained to consider every detail of how something works, or what you need to do and in what order. Instead they are frequently written by the engineers who designed the equipment and who as a result know too much about it! I've no idea whether Siemens uses technical authors or not, they're are big enough (and expensive enough) to afford them, but the simple fact is that you don't always find all the answers there.

If you want to see well written handbooks, go have a look at the DEC PDP11 and VAX handbooks from the '70s, come to think of it the KENT K70 & K90 handbooks of that period weren't bad either - they also used technical authors while I was working for them back then.

Having said that, I appreciate your point where it concerns people who are simply too lazy to go read the manuals, but this doesn't necessarily apply to everybody who asks a stupid question!

Until my next stupid question,

Cheers

Roy
 
Paul and Roy,

Thanks for the cold shower - I'm feeling a lot better now. It's amazing how much vitriol you can squeeze in to a single PS! You know how it's the little things that set you off!

Ken
 
So there!!!

Hey JRW... The S7 instruction list is NOT included with the doc. files that accompany the step7 software. So there!!! ToddM.
 
Instruction list??
Yes it is!!

You better look again or make sure your installation is complete.

PS- Is this coming from the guy trying to figure out the bit search??

Jay
 
Last edited:
kcarlen,

I'm acquainted to AB PLC's (cause I used to work for an American company who uses AB PLC's), my knoledge extended till the 5/40C processors then I quit & join a company with Siemens platform.

I appreciate if u give me some help with ControlLogix, e.g differnces between RSLogix & controllogix...etc or you could choose to send me a stuff of your choice.

In order not to keep the forum busy with this topic, u could choose to e-mail me: [email protected]

Thx in advance
hagos
 

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