stopping plc

[redlinej]

Hi guys i need your help with an issue,i told an engineer that putting a PLC in stop mode completely stop the program from running and when place back in run mode the PLC run the program from a complete start,he said if i take the circuit breaker off to the power supply of the PLC it would do the same thing,but my thought is that data register and retentive timer will save the information in the event of a power failure like taking the C.B off and it would start from where it stop, your input would be very helpful thanks.

 

[itsmoked]

Usually PLCs must 'reboot'. Everything will re-initialize with the exception of those few registers(values) that the code author specifically chose to be retained. Typically just counter values for things like how many cookies or bottles have gone by are chosen to be retained.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[waross]

You have to check the PLC you are using. Even a simple program may not work the same on different PLCs. I had a test program years ago to demonstrate this to students. The location of the program relative to the PLC's memory pages makes a difference also.
There is not one answer to your question as stated.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[controlsdude]

I think your both right on the PLC running a program. But its better not to totally drop power since some things that are barely working will fail on power off/on.

As far as initilizing really depends on the programmer and if he has programmed or configured for init routines from his/her familarity with the plc software or brand of PLC.