siemens plc

jugenzhu1963 · Jun 4, 2006

hi,everybody

I am learning siemens plc(s7-300) now. I don't know how to manipulate the bit memory. For Example how i can make bit M0.0 always ON. Please help me.

Thank you

krk · Jun 4, 2006

SET //Set RLO (to 1)
=M0.0 //Assign to bit

lauu · Jun 4, 2006

M0.0 M0.0
----|/|---------------()-
| |
| M0.0 |
--| |---

SimonGoldsworthy · Jun 4, 2006

Hopefully the two other posts have answered your question. (Another answer is that you can't - if some other processing decides to clear M0.0, then it will be clear until the next time the set instructions are executed)

S7Guy · Jun 4, 2006

Another thing to remember is that an "always on" bit really isn't necessary with Siemens S7. I've written tens of thousands of lines of code, and haven't used one yet. Instead, take advantage of the "SET" and "CLR" commands, which directly affect the RLO.

stplanken · Jun 4, 2006

S7Guy said:
Another thing to remember is that an "always on" bit really isn't necessary with Siemens S7.

Interesting. I use AlwaysOn bits to temporarily bypass one or more contacts in ladder or disable (parts of) a rung, without actually removing any logic. Only in LAD, in STL I have no use for it.

Rack Failure · Jun 5, 2006

[stplanken]Interesting. I use AlwaysOn bits to temporarily bypass one or more contacts in ladder or disable (parts of) a rung, without actually removing any logic. Only in LAD, in STL I have no use for it.

I have done the same as stplanken using always ON (M0.0) and always OFF (M0.1)flags. The flags are set up in OB1. Anyone else do the same?

Homer

rdrast · Jun 5, 2006

Rack Failure said:
I have done the same as stplanken using always ON (M0.0) and always OFF (M0.1)flags. The flags are set up in OB1. Anyone else do the same?

Homer

Hrm... maybe it's just me, but wouldn't it be more intuitive to use M0.0 for the 'Always OFF' state and M0.1 for the 'Always ON' state?

Rack Failure · Jun 5, 2006

Rdast
Oops a typo, should've been more carefull.
BTW how do you do a quote box like you've done? Tried it in my last post but hasn't worked.

geniusintraining · Jun 5, 2006

Rack Failure said:
Rdast
Oops a typo, should've been more carefull.
BTW how do you do a quote box like you've done? Tried it in my last post but hasn't worked.

click here

bkottaras · Jun 5, 2006

Always OFF, always ON

rdrast said:
Hrm... maybe it's just me, but wouldn't it be more intuitive to use M0.0 for the 'Always OFF' state and M0.1 for the 'Always ON' state?

I use the same setup in order to debug as well as enable disable certain functions and rungs of logic on the fly.
Yes, M0.0=always OFF, M0.1=always ON.

siemens plc

jugenzhu1963

Member

krk

Lifetime Supporting Member

lauu

Member

SimonGoldsworthy

Member

S7Guy

Member

stplanken

Member

Rack Failure

Member

rdrast

Lifetime Supporting Member

Rack Failure

Member

geniusintraining

Lifetime Supporting Member + Moderator

bkottaras

Member

Similar Topics