Logix 500 - Setting one bit element inside an integer value

[dlweber]

I admit I did take it the wrong way. However that is my fault for reading to far into it. I t was probably when the word was used a second time, then the Cletus thing (that I didn't even read fully) my mind went off on its only little rant, that I ended up typing.

My jumping to harsh conclusions aside my last post should say
"If they are going to package the compare, mask, and change functions into a pretty little box I would definitely take that option."

But when you put it post 2 I probably seen the abbreviation and didn't read it in detail(even though you did explain it). I am still working at getting the abbreviations down. If I would have read it better I would have seen what you meant. But I made a bad assumption that you were using a abbreviation without explanation therefore would lose me completely. I have read some posts that may have been full of good information I just couldn't understand all of the abbreviations. (again you did explain, I just did not pay enough attention)

But either way no need to apologize it is me who should apologize for my poor assumptions and speaking before thinking.

 

[Ron Beaufort]

I hope that I've been helpful - that is ALL that I intended to do ...

peace ...

 

[TimD]

Wow,

OK, I'll look into the MVM instruction. and interesting to note the latched outputs work on bit-level ints!

Thanks All! Happy Holidays

 

[rootboy]

I'm an AND/OR kind of guy myself (casting further into doubt as to the level of my professionalism )

 

[dlweber]

The need is decreasing with todays hardware, but there are times when doing the code manually can save you scan time and memory, there are some filters I made that I wrote parts in assembly just to shave a few milliseconds off of each set of calculations many applications that is not necessary but when you have a few hundred samples and want to keep up with real time sometimes it is necessary.

 

[rootboy]

Making the transition from the PC world to the PLC world can be harder than it appears. Essentially you have to unlearn your bad habits to make room for our bad habits.

 

[dlweber]

I do miss VHDL though, where all of your code runs parallel, because it isn't code its hardware =)

 

[rootboy]

FPGA's are really cool, I have a couple (Mojo, and various Alteras), kinda hard to wrap my head around though... But like you say, it's all hardware.

It's been a boon for creating new hardware for legacy systems such as the Commodore, Amiga, and MSX to name a few.


I did find this book helpful:

http://www.amazon.com/Verilog-Example-Concise-Introduction-Design/dp/0983497303

 

[Greg Fowlds]

Have you tried an output coil OTE with an address of N7:0/7
Sets or clears one bit of a word.
Other methods suggested seem a bit complicated for only one bit.

 

[dlweber]

I never worked in Verilog, I went straight to VHDL, FPGA I used was Digilent's Nexys2, I used the basys briefly but it didn't have the toys I wanted so I upgraded. Right now my Nexys is DOA I somehow managed to smoke the I/O (J ports) when I was building a FIR...not sure how but by the time I figured it out I was three projects later and was unhappy because I got less than A on those three projects. I was p#$%ed when I figured out I blew the I/O lol

 

[Ron Beaufort]

from Greg Fowlds:

Have you tried an output coil OTE with an address of N7:0/7
Sets or clears one bit of a word.
Other methods suggested seem a bit complicated for only one bit.

Greetings Greg ...

in most cases, you would be absolutely correct – and an OTE addressed for N7:0/7 would indeed be the simplest and most common way to handle this – but back in Post #4 the OP said (among other things):

My HMI can write directly to the integer-bit element, but Logix 500 cannot.

we haven't asked him to explain that statement – but we've all sort of taken it at face value and have been trying to come up with something other than the obvious OTE ...

maybe with some more explanation, the method that you've suggested would sort of "bubble to the top" – but then again, maybe there's something unusual going on with his system that we don't know about ... at least that's what we're all assuming ...

 

[osmanmom]

I’m confuse

Change the BIT means change the WORD

Before the OP write the Mask value he need to know what the Source Value if the Source value Come from HMI

where the Mask/Source value come from?

And where the integer N7:0 source come from?

 

[Doug-P]

Wow,

OK, I'll look into the MVM instruction. and interesting to note the latched outputs work on bit-level ints!

Thanks All! Happy Holidays

Paraphrasing Ron Beaufort, "They're all just bit boxes in the end". Meaning that there's nothing particularly special about latching bits in integers. The term 'integer' is merely a convenience to the programmer to be able to deal with numbers in a more recognizable form. To the processor it's the same as latching bits in a Binary word.

As an example, instead of latching bits in integers or output words you could just as easily work with bits in Timer (except for bit 15!) or Counter presets. With care you can even Unlatch certain Control bits in certain file instructions.

 

[flash053069]

I would use MOV instructions of the decimal equivalent of the bit to be changed into the word to make only the desired bit to go high or low.

 

[Peter Nachtwey]

Can indirect addressing be used in a bit flle?
If so then individual bits can be addressed individually by number using the index register.

My next option would be to use a N file with 16 integers initialized to 1,2,4,8,... 128,256,512....32768. I would use the index register to access the correct word with the desired bit. This should only require loading the index register with the bit number and then doing and OR into the destination word. Simple.