Siemens Step-7 Newbie

Designer · Mar 12, 2005

First scan bit is SM0.1

so in ladder you'd have this



| 

|-----| SM0.1 |----- >>Your instructions

|

Sorry if it looks a little weird, havnt quite got the grasp of posting ladder logic yet lol
Hope this helps, didnt notice if anyone else had posted this so appologies if i stepped on someones post

RMA · Mar 13, 2005

Spot on, brother. The revolution has now just increased its numbers by 100%. We're on the path to righteousness. Let's get some of the big hitters on-board - where are you S7Guy, JesperMP, RMA, Daniel Chartier, JVDCande and the others ...?

Thanks for the compliment, but no way do I deserve to be mentioned in the same breath as the others here! I'm still on the big learning curve, heftily assisted by those other names. Thanks largely to them, I've got to the point where I can occasionally assist others, but I need a few years more experience before I can aspire to membership of this august circle!

With regard to the timers, I'm still in the undecided category. I'm used to S5Timers and somehow the IEC Timers aren't quite so easy - lack of experience on my side perhaps. Recently I've been finding that when the times run in the seconds area, it's sometimes easier to use a Counter that is updated using a 1 Second Merker (Taktmerker), especially when you want to display an increasing time in ProTool.

Sinking Ship · Mar 14, 2005

Hi Imi'ike,

Thank you very much for your reply. It is very helpful to me and Windy. We started with AB SLC and found hard to convert to Siemens S7. But now we are clearer after reading your comments with comparison between them.

Thanks a lot!

Sinking Ship · Mar 14, 2005

Hi Designer,

May I know where can I find this
-----| SM0.1 |-----
in S7?

I neither find it in help file nor the project windows

Thanks.

dchartier · Mar 14, 2005

Hello Sinking Ship;

The SMx.x structure is available only on the S7-200 platform, programmed under Step 7 Microwin. For the S7-300/400, there are no system memory bits; you must use the OBs (OB100/OB101 for start-up logic) to implement first scan bits.

Hope this helps,
Daniel Chartier

Sinking Ship · Mar 15, 2005

Hi dchartier,

Thanks for that. It helps.

Sinking Ship · Mar 15, 2005

I have another question here. Does the scanning method of Step 7 same as AB RSLogix 500?

In AB RSLogix 500 the following can done, which indicates a single pulse:

I:1/2 PULSE PULSE
|--| |-------|/|-------------------( )----|

The PULSE is normally close. When I:1/2 is on the output PULSE will on for 1 pulse. Can this be done in Step 7?

Please advise. Thank you very much.

Designer · Mar 15, 2005

dchartier said:
The SMx.x structure is available only on the S7-200 platform,

I'm not overly familiar with S7/300 onwards as i mainly work with the 200 types, but I wasnt sure whether you were referring to S7/200 or 300 in your first post so i thought i'd throw that in just in case.

Ken M · Mar 15, 2005

Sinking Ship (or can I call you 'SS' for short?)

The effect this produces in S7 is that PULSE will turn on and off on alternate scans, rather than just on for one scan and then off on all subsequent scans. I'm not even sure why you say it would work in RSLogix500.

Let's take the first scan through this piece of logic -

Code:

I:1/2 - false (required state - true)
PULSE - false (required state - false)
result
PULSE - false

Next scan let's have I:1/2 true -

Code:

I:1/2 - true (required state - true)
PULSE - false (required state - false)
result
PULSE - true

Next scan, I:1/2 still true, -

Code:

I:1/2 - true (required state - true)
PULSE - true (required state - false)
result
PULSE - false

Next scan, I:1/2 still true, -

Code:

I:1/2 - true (required state - true)
PULSE - false (required state - false)
result
PULSE - true

and so on, with PULSE alternating true / false.

The S7 solves the ladder network from left to right - does RSLogix500 work like this also?

Regards

Ken.

paraffin power · Mar 15, 2005

SS
Ken's right.
If you're after a oneshot, then you're missing a branch under the code you showed. In AB terms..

XIC I:0.0/0 BST XIO B3:0/1 OTE B3:0/0 NXB OTE B3:0/1

And yes, this would work in Step7.

If you're referring to AB's ONS instruction, then Step7 has this too.
It's 'P' in LAD and 'FP' in STL. That makes sense, Siemens.

Sinking Ship · Mar 15, 2005

Hi Ken & Paraffin,

Oh ya, you are right. I think I quoted a wrong example. The input I put should change to a bit. And this bit will be unlatched when the PULSE "( )" is true. Does this make sense.

So first scan,
bit on,
PULSE NC on
result in PULSE output on.

2nd scan,
PULSE output on,
bit off,
PULSE NC off,
PULSE output off.

And this makes sure the PULSE is only one pulse, doesn't it?

But anyway, you two have cleared my doubts. As long as it can work in Step 7 I am satisfied already. Guys, thank you very much!

Sinking Ship · Mar 17, 2005

Hi guys,

Can anyone advise me on how to write a network that result in blinking indicator?

In AB RSLogix 500 I will do the following:

I:1/5 S:4/6 O:5/0
|---| |-----------| |---------------------------( )---|

May I know how to do this in Siemens Step-7?
Can I find this S:4/6 (Time base) in Siemens Step-7?

Thanks for your advice.

SimonGoldsworthy · Mar 18, 2005

With S7 317,318 etc, you have to provide your own flashing/blinking program. I call an FC that generates 3 different blink rates and assign the different blinks to Global flags e.g. M1.0, M1.1, M1.2 which you then use throughout your blocks. The source code for the blinker is below:

FUNCTION FC 6 : VOID
TITLE =Blink generator
VERSION : 0.1

VAR_OUTPUT
bBlink1 : BOOL ;
bBlink2 : BOOL ;
bBlink3 : BOOL ;
END_VAR
VAR_TEMP
mytime : TIME ;
END_VAR
BEGIN
NETWORK
TITLE =Generate blinks

CALL SFC64 (
RET_VAL := #mytime);
A L 2.2;
= #bBlink1;
A L 2.1;
= #bBlink2;
A L 2.0;
= #bBlink3;
END_FUNCTION

JesperMP · Mar 18, 2005

Sinking ship and Simon,
I suggest that you check the CPU property "Cycle/Clock Memory" tab .. "Clock Memory".
This function is also available on 317 and 318 CPUs.

RMA · Mar 18, 2005

Here you are.

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