Online status of STL code in Step 7

Hi All,

I'm looking for some basic help on operating Step 7 Version 5.3. Ive connected to an S7-400 PLC on our ethernet network using the above software and can monitor the blocks. I'm not an STL programmer and am used to ladder and the blocks contain a mixture of STL and LAD. My question is:

when monitoring the LAD online the rungs turn green to indicate the power flow through the networks but how do I tell what the STL is doing? i.e. the status of the addresses in the STL. All I can see is the STL code which doesn't change in appearance wether i'm online or offline.

Sorry if this sounds a bit dense but my programming experience is with AB equipment and this Siemens stuff has always seemed a bit Alien!

Cheers,

Lee

For statment list, you need to look at two things, when dealing with boolean logic the RLO, when dealing with bytes, words etc the accumulators. There are other status bits but in general the RLO is the main.

These can be seen on the right of the STL code, sometimes its easier to move the boundary closer to the code, to ensure your lining the right things up.

The RLO is what decisions are made of and the logic sets or resets the RLO.

example

M 2.0 = Off
M 2.1 = On
M 2.2 = On
M 2.3 = Off

Code-----------RLO
A M 2.0_________0
A M 2.1_________0 (M 2.0 and M 2.1 are in series so M 2.1 has no effect)
O
A M 2.2_________1 (Its OR'd so the RLO becomes 1)
AN M 2.3________1
= M 2.4_________1 (RLO is '1' so M 2.4 turns ON)

example 2
M 2.0 = On
M 2.1 = On
M 2.2 = On
M 2.3 = On

Code-----------RLO
A M 2.0_________1
A M 2.1_________1
O
A M 2.2_________1
AN M 2.3________0
= M 2.4_________1 (RLO is still '1' as the previous result was OR'd so M 2.4 turns ON)

example 3
M 2.0 = Off
M 2.1 = On
M 2.2 = On
M 2.3 = On

Code-----------RLO
A M 2.0_________0
A M 2.1_________0
O
A M 2.2_________1
AN M 2.3________0
= M 2.4_________0 (RLO is '0' so M 2.4 turns OFF)


For the accumulators, I can't remember if both are shown automatically, if not I think its right click over the area and choose what you see. The thng to remember for comparisons etc, what is in Accu 2 is what is being compared against Accu 1.

example

MW6 = 5
MW8 = 100

Code-------RLO------ Accu1 ----------- Accu 2

L MW6_____dont care___5_________________dont care
L MW8_____dont care___100_______________5
<I__________1_________100_______________5 (5 is less than 100)
= M 2.0_____1_________100_______________5 (M 2.0 comes on)

example 2

MW6 = 5
MW8 = 100

Code-------RLO------ Accu1 ----------- Accu 2

L MW6_____dont care___5_________________dont care
L MW8_____dont care___100_______________5
/I________dont care___20_______________5 (divide 100 by 5)
T MW10____dont care___20_______________5 (20 transfers into MW10)

To be honest in the last example, can't remember if accu 2 remains unchanged, it may zero, it used remain unchanged in S5, something in my mind tells me it could zero in S7 though?? try it and see really.

When you monitor, a pane appears on the RHS of the screen showing various data values. Note that you can drag the left hand pane fully to the right so the right hand pane may be covered up. Use the mouse to drag the left hand panes right hand edge to the left to reveal the right hand pane.
You can customise what is shown on the right hand pane (right click in this area) but normally the columns shown are RLO (result of logic operation), STA (the boolean status of the current addressed variable), STANDARD (the value in accumulator 1).
If there are no values shown then this means the lines of STL you are monitoring are not being processed.

(NB: cross post with PeterW)

What accu2 called, that may help him as well, I do it automatically most times and can never remember unless its front of me on-line.

If you right click on the right hand pane, then show, the option is Accumulator 2. When showing, the column is labelled "Accu 2"
Right click on the relevant column then hide will turn it off.

Simon / Peter,

Thanks for the help! It was indeed just a case of moving the panes about and i've added the ACCU2 2 so all has become clear!

Thanks for the quick response!

Cheers,

Lee