first time using cpt instruction

trying to use a cpt instruction to enter the following

(n7:0/9000)*100

how do you enter the divide symbol?
that appears to be what I am doing wrong

| The "pipe" symbol, shift of "\"

(n7:0|9000)*100

Thanks

Watch for roundoff error if you are storing that result in an N file. If you are and the range of N7:0 allows it, you are better off doing N7:0 * 100 | 9000.

Also, if you are saving the result to a floating point register then enter your constants as floats. N7:0|9000.0*100.0.

It looks like you are performing a percentage calculation, so if you must use integer math and N7:0 < 9000 then N7:0 | 9000 will be less than 1 - which will round to just 0 or 1 with integer math, giving you only 100 or 0 as your answer (This is what Robert was refering to). In this case you should re-arrange the equation to multiply by 100 first, then divide by 9000, or enter the constants as floats (ie 9000.0 and 100.0) even if you are storing the result in an integer.

Last, a word about constants and the CPT instruction. The CPT instruction takes longer to execute than single operation math instructions, but it is faster for longer computations because it doesn't have to take time to store and fetch intermediate results from memory. Where you are using constants, combining the two constants and using a single MUL or DIV instruction will be more efficient, ie N7:0 * 1.11111111e-2, or N7:0 | 90

thanks alot

never used the cpt instruction before, most of the things that i have done, i have been able to use the scp instruction.

I searched a slc500 instruction manual that I have as a pdf file, and was unable to find in it how to put the proper symbols in.

This site is great

irondesk40 said:

thanks alot

never used the cpt instruction before, most of the things that i have done, i have been able to use the scp instruction.

I searched a slc500 instruction manual that I have as a pdf file, and was unable to find in it how to put the proper symbols in.

This site is great

Click to expand...

Don't know about the PDF, but it is in RSLogix500 CPT help:

Expressions - The expression is zero or more lines, with up to 28 characters per line, up to 255 characters. Instructions that can be used in the Expression include: +, -, *, l (DIV), SQR, - (NEG), NOT, XOR, OR, AND, TOD, FRD, LN, TAN, ABS, DEG, RAD, SIN, COS, ATN, ASN, ACS, LOG, and ** (XPY). The execution of a CPT instruction is longer than a single arithmetic operation and uses more instruction words.