CIP 16bit Integer Array what is each bit value

[Rusty]

The analog array has 16 individual bits and each bit is an alarm.
SCADA is having issues getting the BIT bool value.

However they can get the analog value.
Is there a way to calculate which bits are on based on the integer array value?

If bits 1, 3, and 14 are on you would get a value that is different than if bits 2,9 and 11 were on.

How could they figure out what alarms are on based on the value?

I wish they could get the bit values. The Alarm array tag bits just won't respond as Alarms_Plant[0].0, if you have any ideas folks please let me know.
Thank You ALL

 

[ASF]

Welcome to the forum!

What SCADA platform are you using? Most likely you'll have to use some kind of script to extract the individual bits, and the specifics of that will be application-dependent.

 

[Rusty]

Thank you I should have said. It is an Allen Bradley ControlLogix L34

 

[ASF]

That's the PLC, we need to know what the SCADA platform is.

(also, "L34" doesn't really match up with any type of Control Logix, but that isn't really the issue here - the SCADA is where you'd be looking to extract the bits)

 

[drbitboy]

If the scada cannot look at individual bits e.g. sixteenbits.0, perhaps it has a scripting language that has a bitwise AND operator. So for bit 0 you would so something like

sixteenbit0 = sixteenbits AND 1 ;;; or AND 0x0001
​

for bit 10 you would do

sixteenbitA = sixteenbits AND 1024 ;;; or AND 0x0400
​

for bit 15 you would do

sixteenbitF = sixteenbits AND -32768 ;;; or AND 0x8000
​

After that, you would check the value of the result e.g. if sixteenbitA is 0, then bit 10 of word sixteenbits is 0; if sixteenbitA is non-zero, then bit 10 of word sixteenbits is 1.

 

[robertmee]

If the Scada is Ignition, it doesn't natively read bits of words, but you can create them using UDTs in ignition.

Most other popular Scadas like Wonderware, iFix, FactoryTalk, etc can access bit of words using the correct delimiter and syntax. So as has been mentioned, what Scada are you using?

 

[parky]

Trying to put it simply, each bit of a word is usually known as the base of 2
As already posted, bit 0 is decimal 1, bit 1 is decimal 2 bit 3 is decimal 4 so in effect the higher the bit the higher the number value so from bit 0 to 15 it goes
1,2,4,8,16,32,64,128,256,1024,2048,4096,8192,16384,32767, 65535
So if bits 1 & 3 are on that is 1+4 = 5
To extract there are many ways, in-built functions that convert the 16 bit number into individual boolean bits, you can build your own with a script or PLC ladder, it's just a matter of creating a loop, AND the word with 1 transfer that to a boolean bit, shift right the word by 1, loop back & do it again, do this a total of 15 times (16 but the first is no shift).
so your question does the decimal value change depending on which bits are on is yes the one thing you have to remember is that a 16 bit word can be represented as a signed word -32767 to +32767, an unsigned word is 0 to 65535 as the word is representing 16 boolean bits then it can be considered a unsigned word.

 

[drbitboy]

bit 3 is decimal 4
...

So if bits 1 & 3 are on that is 1+4 = 5

http://www.plctalk.net/qanda/showthread.php?p=68241#post68241

 

[parky]

oops bit of a missprint there forgot about it is actually bit 0

 

[robertmee]

oops bit of a missprint there forgot about it is actually bit 0

Unless it's a TI PLC. Then it's bit 16 to bit 1. Always confusing mapping between TI and AB.