Best instruction for 256 inputs

[AgentGx42]

I am working with an AB PLC5
I need to scan 256 inputs that are normally high
if one drops low then take action but continue scanning for others.

I been trying to us the FBC instruction but can seem to get it right.

Question: What is the best instruction for a large number of inputs?

Is using the FBC on the right track or is there a better way?

Any help is appreciated. Thanks in advance.

 

[OkiePC]

How about a NEQ, EQU, or MEQ operating on 16 at a time?

Example:
NEQ(Not Equal)
Source A: I:12
Source B: N100:12

Where N100:12 is populated with the bit pattern you wish, or could be a constant.

If there are input points within actual slot/groups that you want to ignore, use the MEQ and put a zero in the bit positions you want to ignore.

After the NEQ, you can set a bit, to cause whatever action you want later on, and depending on your needs, maybe copy the new value of the input word into your compare Source B for the next scan.

Using the EQU or MEQ, the instruction would be true under normal circumstances, and then go false when you needed to take action.

Does this help?

 

[Ken Moore]

Okie's idea would work if it doesn't matter which bit is low.
If all the bits in one word were high the decimal value would be -1.

Do you need to know exactly which bit is low?

What if two or more are low?

 

[SNK]

What is the problem with the FBC?
It is pretty straight-forward.
There are examples, I beleive in the Instruction Set Manual.