Newbie to the site with newbie questions

Hello everyone,

I've been reading for a few days and trying to absorb as much as I can as I'm neither a PLC programmer and don't have any experience with instrumentation.


Basic question,true of false : a plc (specifically melsec FX1s) stores a program in an compiled form (binary) and doesn't store the actual code. In other words if I plug in a laptop with the proper software, drivers, etc. I will not be able to read or modify the existing program. All I can do is upload a new program.

Simple I hope.

Thanks a lot
Kal

False
I cant speak to that specific PLC but in general you are half right. The code is generally loaded (I wouldn't always call it compiled) in some fashion but can be read by programs designed to do that.

Thanks a lot. Is the program designed to do that the same as the program that was used to write the code?
If we use Gx Developer for melsec or rslogix for Allan Bradley (i think) do we use the same software to edit the code?

Thanks

That's right.

A small note too regarding "uploading" and "downloading", which is important to get right (especially if you're doing it to a running machine!):

- "Uploading" the program means you are extracting the program from the PLC to display on your laptop
- "Downloading" the program means you are transferring a program from your laptop into the PLC

The way I was taught to remember it is to put the two devices on a page with the "smartest" one on top. Obviously, your laptop is smarter than your PLC - the laptop creates the code, the PLC just executes it - so if you're going from laptop to PLC, you're going DOWN the page; hence DOWNLOADING.

I was told by a co-worker once to just visualize you put your laptop on top of the PLC rack, then the upload/download is easier to remember.

ASF said:

That's right.

A small note too regarding "uploading" and "downloading", which is important to get right (especially if you're doing it to a running machine!):

- "Uploading" the program means you are extracting the program from the PLC to display on your laptop
- "Downloading" the program means you are transferring a program from your laptop into the PLC

The way I was taught to remember it is to put the two devices on a page with the "smartest" one on top. Obviously, your laptop is smarter than your PLC - the laptop creates the code, the PLC just executes it - so if you're going from laptop to PLC, you're going DOWN the page; hence DOWNLOADING.

Click to expand...

UPLOAD/ DOWNLOAD what you have suggested is for AB and some others, different PLC"S go the other way round. GE FANUC if l remember correctly is one.

For many programs you will loose comments and symbols/tags if you download/upload FROM PLC when not having original program. This can very well make the program unreadable.

Thanks a lot everyone. Much appreciated.

duckman said:

UPLOAD/ DOWNLOAD what you have suggested is for AB and some others, different PLC"S go the other way round. GE FANUC if l remember correctly is one.

Click to expand...

I've not come across one yet, but I'll take your word for it the only GE Fanuc I've ever seen was one where to transfer a backed up program into the controller, you got an audio cassette, and a cassette player, plugged a 3.5mm audio cable into the headphone jack of the cassette player and the front of the PLC, set the volume of the cassette player just right (there was a little paint mark at the right spot on our, er, "programming laptop"), and press play. So it's quite possible that upload/download was the other way around, but all I knew about was "play" or "record"

Just to satisfy my curiosity, does anyone know of any other PLC's that have upload/download the other way around?

No, but your other description sounds much like my first TANDY TRS80 (16k)

It had a cassette player that you plugged into it, we would type code we got from a book for hours, and after all that work end up being able to play a game equivalent to pong.

Thinking back that had to be 1978 or 79, good memories.