RobCNC

Can anyone explain the difference between P-trig and P?

They both scan RLO for a change from 0 to 1 at the input and seem to do exactly the same?

So I would like to know which one to use to make a memory bit '1' for 1 cycle.

Thanks in advance for your response.

FLANKS

hdhosseini

For reason of using Positive (Negative) edges,please read the
following thread:

use positive edge

A detailed description of different types of Edge evaluation instructions
(in LAD or FBD)are available here:
Positive and negative edge instructions


3 different types of edge functions can be categorized for S71200:


1- Edge evaluation with contacts.State of this contact is "True" when
a positive(or negative) edge sensed in input signal (signal in upper side
of contact) and memory in downside is used to keep last status of input.
The status of contact is combined with input signal status and generate
the output signal status.As an Example, using these contacts in set and
reset input of a flip-flop.

IN
|-------|P|----
MEMORY



2-Edge evaluation with coils,status change of signal entering the coil
is used to create short pulse in OUT signal on the coil.This output
signal can be used in the rest of logic (e.g by a contact).

OUT
-------(P)
MEMORY



3-Edge evaluation via Q-boxes.2 Q-box functions (P_TRIG and N_TRIG) are
used to check edge change in current flow before the box(CLK input) and
short pulse in "Q" output.These boxes also need memory to keep the current
status of the input.



More information available in the provided link.

RobCNC

Thanks for your reply, but I still do not understand the difference completely.

I've used |P| in an S7-300 program to make a Resetsignal for 1 programcycle.

Something like:

A I 1.0 //Resetbutton

FP M1.0 //memorybit

= M 2.0 //Resetpulse

Then I use M 2.0 as resetsignal so the operator can't fake it by keeping reset button pressed. The problem is that it looks like M 2.0 loses it's state halfway programcycle. In some places (in the program) the error get's reset and in some places it doesn't.

Will this work better when I use P-trig?

RobCNC

I've checked all other possiblities. But none of them accure.

The bit 'set' by the edge detection just doesn't work through the complete cycle.

But this is not really a problem anymore, I just made the same edgedetection halfway and now it works.

But what I want to know, and still do not understand, what are the differences between P and P_trig? I'm using S7-300 so does are the only 2 options I can use. There should be any difference I think?