Mitsubishi Beginners question - System Reset

Hi all,

I am completely new to PLC's and their programming, having started a new course at college. Part of the course is to write a simple program in GX developer.

Without giving away too much, as I am determined to do the program myself, the brief states that the system should be "reset" before running - meaning that the timers and counters should all be reset before the program runs proper.

I am at least aware of the "rst" function, but I was wondering if there was a simpler way of resetting several timers and counters similtaneously, or if each has to have its own reset line?

Any advice would be much appreciated guys, thanks.

Non-retentive timers reset automatically, when the timing condition is false.
Also, non-retentive timers and non-latched counters reset on the PLC operation start (not necessarily on power up, but also on switching from stopped to run).
Retentive timers and all counters must be each reset programmatically, according to its operation logic.
It is possible to reset an entire group of consecutive timers or counters with ZRST instruction.

"The system should be "reset" before running - meaning that the timers and counters should all be reset before the program runs proper"- is too generalized statement and is not correct.
For instance, why should you reset a production totalizer or runtime totalizer counter, if they are created to never be reset.

Thanks for clarifying Sergei.

I realise the brief is lacking in detail, but it has more to do with the level of the course I think. It is literally a beginners introduction.

Phrases such as "retentive" I understand because of the studying and research I have done myself, but nothing so detailed has came up in the course so far.

Thanks again for the reply though. It's pointed me in the right direction.

A system reset is often done on the first line of a program. Commonly termed 'house keeping' Where any variables or bits that need to be set to zero are done.

As has been said ZRST will reset a range of bits or words to 0

The usual way to do this is --|M8002|------------------[ZRST M0 M40]
and --[ZRST D100 D200] etc

Where M8002 is a N/O contact that 'pulses' once on the initial scan

Thanks very much Ronnie. Doesn't get clearer than that.

I had finished the program, but I think I'll go back and change it now. As Sergei mentioned, I believe the timers and counters I've used are non-retentive anyway, but if the brief asks for a reset, who am I to argue?

I'm on my phone at the moment, but I'll try to upload the brief and finished program later, just for a little feedback if you have the time?

Either way, thanks for the advice mate. Appreciated.