
8-21
Ladder Logic (LAD) for S7-300 and S7-400
C79000-G7076-C504-02
8.20 Address Positive Edge Detection
The Address Positive Edge Detection instruction compares the signal state of
<address1> with the signal state from the previous signal state check stored
in <address2>. If there is a change from 0 to 1, output Q is 1. Otherwise, it
is 0.
Certain restrictions apply to the placement of the Address Positive Edge
Detection box (see Section 6.1).
Table 8-19 Address Positive Edge Detection Box and Parameters
LAD Element Parameter Data Type Memory Area Description
<address1> BOOL I, Q, M, D, L
Signal to be checked for a
positive edge transition.
POS
M_BIT
Q
<address1>
<address2>
M_BIT BOOL Q, M, D
The address M_BIT indicates
the edge memory bit that stores
the previous signal state of POS.
Use the process-image input (I)
memory area for the M_BIT
only if no input module already
occupies this address.
Q BOOL I, Q, M, D, L One-shot output
Status Word Bits
BR CC 1 CC 0 OV OS OR STA RLO FC
Write x – – – – x 1 x 1
I 0.0
Output Q 4.0 is 1 if the following
conditions exist:
S The signal state is 1 at inputs I 0.0
And I 0.1 And I 0.2
S And there is a positive edge at
input I 0.3
S And the signal state is 1 at
input I 0.4
I 0.2I 0.1
I 0.3
POS
M_BIT
Q
M 0.0
Q 4.0
I 0.4
Figure 8-19 Address Positive Edge Detection
Description
Bit Logic Instructions
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