Addressing a thumbwheel switch in Rslogix 500

Hello, I'm trying to design and build a new PLC trainer. I recall from college (4 years ago) that we had a three digit thumbwheel and a three digit display. We were using a PLC5 and RSLogix5. I know that every digit requires 4 inputs or outputs, I understand that. We used two slot addressing with 16 point I/O modules. At school when we needed to use the thumbwheel or display we would address them I:001 and O:001 respectively. I also understand how these two I/O's are wired the the input and output cards - the LSD bit is wired to I:001/0 and the MSD bit is wired to I:001/13, same for the outputs O:001/0 to O:001/13.
We would use the FRD instuction to trasfer the input # into a integer value. To do this we addressed the FRD's source as I:001 which was the address for the thumbwheel. The same for tranfering a integer value to the output display we would use the TOD instruction and its destination address was O:001 again which was the output displays address.

In Logixpro you do simalar addressing to use the thumbwheel and display, which is:



In both programs you do not have to address each individual bit on the card.
Can this addressing be done with RSLogix 500 and a SCL500 PLC? If I have a digital input and output card and I wire a BCD thumbwheel switch and a display can I address them the same way? Or what are the options? If the cards were in say slot 5 and 6 respectively what do I address them with? I:5.0 and O:6.0 as in the pdf attachment?

It makes it simple to use only 1 FRD instruction to address a input, and only 1 TOD instuction to address a output display.

It seems that you are addressing the card in a slot and not a individual terminal. ??

Thanks, I hope I explaned myself as do I hope you understand what I'm asking.
John

Looks like you have it right. The SLC works like the PLC-5 in that you use the word address of the card not the specific bits. Essentially you are addressing an "analog value" read from/sent to the digital I/O card.

OG

Thanks OG,

I have this fear that when I hook this idea up, I destroy something or send the processor into fault. I've invested alot of $ into my PLC hobby and I'd rather not waste time and $.

John

Greetings John,

as OG said, it looks like you're on the right track ... quick question: this time around do you have 4 digits on each of your thumbwheel and display devices? ... or just three (or less) like the system you mentioned from college? ... if the answer is anything less than 4 digits, then you might want to take a look at the MVM (Masked Move) instruction ... by using this approach, you might be able to "reclaim" the unused input and output bits that would otherwise be wasted ...

going further: this link covers some more information about thumbwheels and displays ... the "strobing" experiment makes a good "beyond beginner" learning exercise - if your equipment will support it ...