RSLogix5000 Aliasing Help

Hello, I am new here, but I have a question about programming RSLogix5000.

I know how to aliasing tags, but I thought there was a way to aliasing bits of tag? For example, I am trying to alias an output to a bit of an INT.

I would like to do this so I can only allow rungs to be active, when the tag is a certain value. For example, when the tag is equal to 7 or the bits 00000111, then the rung will be true.

I hope someone can help me with this or at least let me know if what I want is just not possible with RSLogix5000.

Sure you can do this.

I think you're wanting to make a new BOOL that aliases a bit in an INT. Right?

If so, make your new BOOL, then set the alias to INT_TAG.0 (for bit 0 of integer INT_TAG. .1, .2, .3, ... for other bits within the word.)



In this example, B01_LSL_ALM is a BOOL that is bit 0 in the 11th word of an DINT-array called ALM.

Thanks for your reply, but what I am trying to do is alias to a input.
Tag Data Type
Position INT
Position.0 BOOL
Position.1 BOOL
Position.2 BOOL
Position.3 BOOL
Position.4 BOOL
Position.5 BOOL
Position.6 BOOL
Position.7 BOOL
[...]

I now want to alias a controller tag, let us say a 1791D-16B0, but it could be any input module.

Tag Data Type Alias
Position.0 BOOL ...I.Data[0].2

Ohhh... I don't think you can do that.

But you ~can~ alias a whole DINT to a whole input module. Then you would just reference the input_module_alias.0 within your program.

Or better yet (though it takes a little bit of programming) is to map your "real" inputs/outputs to individual bits. Then, if you ever need to move an input or an output, then you only have to make the change in one place of your program.

example:


Here, I'm mapping inputs to specific bits in an array called MI (short for "mapped inputs"), then each of the specific bits are assigned an alias that has a real-function name.

If, for whatever reason, I ever need to move the UNIT 2 DISCHARGE PUSHBUTTON to a different IO point, then this is the only place I have to make a program change.

Others here do this as well, though they tend to map a whole input module to a DINT all in one MOV or COP instruction. I prefer to do it bit-by-bit because I have the flexibility of moving IO if needed. (And occasionally, I've had IO points fail or someone hooks something up wrong or...)