Number of Nonzero bits in a Word
- Thread starter grockk
- Start date
Mark Buskell
Member
You could probably set up some ADD logic and look at the bit level of the Dint. Set the result to zero at the beginning of the scan. If Dint.0 = 1 then Add 1 to result.If Dint.1 = 1 then Add 1 to result and so on. At the end result in your example would be 3.
You could also do it with some loop logic and indirect addressing for the bit but that gets a little more complicated.
You could also do it with some loop logic and indirect addressing for the bit but that gets a little more complicated.
TConnolly
Lifetime Supporting Member
You can search the forum for "bit hacks" and find a few clever methods but none of them will execute faster, or be faster for you to program, than a brute force subroutine.
CLR NUMBITS
SOR XIC MYDINT.0 ADD 1 NUMBITS NUMBITS EOR
SOR XIC MYDINT.1 ADD 1 NUMBITS NUMBITS EOR
SOR XIC MYDINT.2 ADD 1 NUMBITS NUMBITS EOR
.
.
.
SOR XIC MYDINT.31 ADD 1 NUMBITS NUMBITS EOR
CLR NUMBITS
SOR XIC MYDINT.0 ADD 1 NUMBITS NUMBITS EOR
SOR XIC MYDINT.1 ADD 1 NUMBITS NUMBITS EOR
SOR XIC MYDINT.2 ADD 1 NUMBITS NUMBITS EOR
.
.
.
SOR XIC MYDINT.31 ADD 1 NUMBITS NUMBITS EOR
Mark Buskell
Member
Then I guess you have a lot of typing 
The above examples don't care how many words you have. They are basically looking at at boolean. Either on or off.
The above examples don't care how many words you have. They are basically looking at at boolean. Either on or off.
hd_coop
Lifetime Supporting Member
Program an add-on instruction.
I am not familiar with controllogix.
This is one simple code written in C
long count_bits(long n) {
unsigned int c; // c accumulates the total bits set in v
for (c = 0; n; c++)
n &= n - 1; // clear the least significant bit set
return c;
}
I hope you are able to translate it to your language
This is one simple code written in C
long count_bits(long n) {
unsigned int c; // c accumulates the total bits set in v
for (c = 0; n; c++)
n &= n - 1; // clear the least significant bit set
return c;
}
I hope you are able to translate it to your language
TConnolly
Lifetime Supporting Member
You can program a FOR-NEXT loop but it will execute slower than a brute force subroutine, and if you aren't an experienced programmer it will take you more time to program the loop. In the amount of time spent on this thread you could have completed the task and moved on.
If you want to enter the rungs really fast then open a text editor and paste the mnemonics "SOR XIC MYDINT.0 ADD 1 NUMBITS NUMBITS EOR " for 32 rungs without any line returns. In the text editor increment the bit number MYDINT.# for each of the bits. Then in RSLogix open the mnemonic editor by double clicking on the rung number for a blank rung. The mnemonic editor line will open at the top of your screen. Paste in the entire long string from the text editor and press enter. RSLogix will paste in 32 rungs.
Have you searched the forum on "bit hacks" yet? We've discussed bit counting schemes ad-naseum here.
If you want to enter the rungs really fast then open a text editor and paste the mnemonics "SOR XIC MYDINT.0 ADD 1 NUMBITS NUMBITS EOR " for 32 rungs without any line returns. In the text editor increment the bit number MYDINT.# for each of the bits. Then in RSLogix open the mnemonic editor by double clicking on the rung number for a blank rung. The mnemonic editor line will open at the top of your screen. Paste in the entire long string from the text editor and press enter. RSLogix will paste in 32 rungs.
Have you searched the forum on "bit hacks" yet? We've discussed bit counting schemes ad-naseum here.
Last edited:
TConnolly
Lifetime Supporting Member
For more info on making large numbers of similar rungs really fast see this thread: http://www.plctalk.net/qanda/showthread.php?t=53235
BTW, welcome to the forum.
BTW, welcome to the forum.
Last edited:
Then I guess you have a lot of typing
The above examples don't care how many words you have. They are basically looking at at boolean. Either on or off.
Using a text editor made this a lot easier 160 rungs was as easy as a few find a replace in notepad.
TConnolly
Lifetime Supporting Member
Make sure you stick all that in a subroutine so that you don't have to slog you way through it just to find some other piece of code in the future. In the subroutine once its debugged you can forget about it and never look at it again.
did someone say :
reset count,
Begin loop
Compare LSB with =1, if true , add one to alarm count
Then shift right 1
Loop 31 times or 15 or how ever many bits you want to check.
Run the loop every scan, never miss a bit.
You can also keep track of which bit is true and look at the loop count to see which alarm is on, not just how many alarms are true.
Then do some action.
160 rungs???????????????
reset count,
Begin loop
Compare LSB with =1, if true , add one to alarm count
Then shift right 1
Loop 31 times or 15 or how ever many bits you want to check.
Run the loop every scan, never miss a bit.
You can also keep track of which bit is true and look at the loop count to see which alarm is on, not just how many alarms are true.
Then do some action.
160 rungs???????????????
Rube
Member
I would only call that subroutine when the word is greater than 0--not every scan...
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