Start, Stop And Latching; Example 1: The Latching Circuit For Priority Of Stop; Example 2: The Latching Circuit For Priority Of Start; D.3.4 The Example For Designing Basic Program - Delta Electronics AC Motor Drive VFD-E User Manual

Appendix D How to Use PLC Function|
on analyzing other ladder diagram. You can recognize the command MRD by the symbol
"├".
9. MPP command is used to read the start status of the top level and pop it out from stack.
Because it is the last item of the horizontal line, it means the status of this horizontal line
is ending.
You can recognize this command by the symbol
"└". Basically, that is all right to use the above
method to analyze but sometimes compiler will
omit the same outputs as shown at the right.

D.3.4 The Example for Designing Basic Program

Start, Stop and Latching

In the same occasions, it needs transient close button and transient open button to be start
and stop switch. Therefore, if you want to keep the action, you should design latching circuit.
There are several latching circuits in the following:

Example 1: the latching circuit for priority of stop

When start normally open contact X1=On, stop
normally contact X2＝Off, and Y1=On are set at
the same time, if X2=On, the coil Y1 will stop
acting. Therefore, it calls priority of stop.

Example 2: the latching circuit for priority of start

When start normally open contact X1=On, stop
normally contact X2＝Off and Y1=On (coil Y1 will
be active and latching) are valid at the same time, if
X2=On, coil Y1 will be active due to latched
contact. Therefore, it calls priority of start.
D-14
MPS
MRD
MPP
Y1
X1
X1 X2
Y1
Revision June 2008, 04EE, SW--PW V1.11/CTL V2.11
MPS
MPP
X2
Y1
Y1