hour counter instruction (rslogix 500

I used a RTO with 3600 sec , but used a add 1 to display , but the only problem is I don't won't to reset and a add instrution. Value goes up to 37268? Any ideas
 
OkiePC said:
Dang I wish they'd give me 3.5 years...
Click to expand...

That would be just about right.

Its been 1365 days since 4/27/09, or 32760 hours. Seven hours into the day and an N word is maxed out.

That is why an L address is recommended instead of an N address. An L address will out last the PLC at ~1/4 of a million years. 🍺
 
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I was under the impression that the add instruction only goes up to 32768 +/- or is it the n address that only goes up to 32768
 
It has nothing to do with the math instruction.

N address are 16 bit integers. The range of numbers that you can represent using a 16 bit N word is -32,768 to +32,767.

To represent a larger number you need to use more bits.

L addresses are 32 bit integers. The range of numbers that you can represent using a 32 bit L word is -2,147,483,684 to +2,147,483,683
 
TConnolly said:
The range of numbers that you can represent using a 32 bit L word is -2,147,483,684 to +2,147,483,683
Click to expand...

Small correction : 32-bit signed integer range is -2,147,483,648 to +2,147,483,647

It might make a difference to someone....

Interesting that the last digits are always 8 and 7 when the number of bits is wholly divisible by 8.

08 bits -128 to +127
16 bits -32,768 to +32,767
24 bits -8,388,608 to +8,388,607
32 bits -2,147,483,648 to +2,147,483,647
40 bits -549,755,813,888 to 549,755,813,887
etc.

I'm sure there must be a proof that this will always be the case, but it is beyond my maths capabilities to postulate one.
 
stu said:
I was under the impression that the add instruction only goes up to 32768 +/- or is it the n address that only goes up to 32768
Click to expand...

stu the ADD instruction on a 16-bit PLC (like SLC) works to (signed) 16-bit precision, on a 32-bit PLC (like Logix5000) it works to (signed) 32-bit precision.

You will get Overflow flag being set, if the add causes the result to exceed thw maximum positive value allowed, or if the destination data-type is "too small" to hold the result.
 
I plugged 231 into my calculator and looked at the right number and my lysdexia kicked in and I typed 84 instead of 48 o_O I double checked what I typed and saw 48, such is the nature of the human brain. Then I copied and pasted and subtracted 1, perpetuating the mistake. Thanks for catching that Daba.

cant_sleep.png
 
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