Binary

I have two inputs, 8 bits each input, combine together to give me -32767 to 32767 decimal. In RS 5000, what operation can I use to combine it together in to a 16 bits group instead of 8 bits each input. Because the value will varies between -32767 to 32767 so how can I combine these two group together and converter to signed decimal number. Please Help! I really appreciated.

Example.
Local:I.Data[0]
0 1 2 3 4 5 6 7
Local:I.Data[1]
0 1 2 3 4 5 6 7

You can use the COP instruction to move these two SINT elements into a single INT element.

COP
Source Local:I.Data[0]
Destination Integer_Value
Length 1


The tag "Integer_Value" must be an INT type.

The Length is =1 because the Length of a COP instruction in RSLogix 5000 is the number of destination elements.

You will end up with Local:I.Data[0] in the lower 8 bits of the 16-bit Integer_Value tag, and Local:I.Data[1] in the upper 8 bits of the 16-bit Integer_Value tag.

Ken Roach said:

You will end up with Local:I.Data[0] in the lower 8 bits of the 16-bit Integer_Value tag, and Local:I.Data[1] in the upper 8 bits of the 16-bit Integer_Value tag.

Click to expand...

Yes nhatpham, be sure you have the 8-bit bytes the correct way round, as Ken has posted.

If they are wired "wrong" and your upper 8-bits are wired to Local:I.Data[0], then you can do either of the following...

1. Rewire your I/O

2. Use 2 BTD instructions to copy the bits from your source SINTs into the INT in the correct order.

3. Do the COP as Ken has suggested, but to a temporary INT, and then execute a SWPB (Swap Byte) instruction to swap the bytes into your final destination.

I would go with either 2 or 3, most likely 3.

Thank you very much.

How is the COP instruction moves data[0] and data[1], if we only using one source in your case data[0]. Or do I have to create another COP instruction for data[1] and length to be 2?
Sorry, I'm new to RS5000. But I really appreciate your help.

daba said:

Yes nhatpham, be sure you have the 8-bit bytes the correct way round, as Ken has posted.

If they are wired "wrong" and your upper 8-bits are wired to Local:I.Data[0], then you can do either of the following...

1. Rewire your I/O

2. Use 2 BTD instructions to copy the bits from your source SINTs into the INT in the correct order.

3. Do the COP as Ken has suggested, but to a temporary INT, and then execute a SWPB (Swap Byte) instruction to swap the bytes into your final destination.

I would go with either 2 or 3, most likely 3.

Click to expand...

I'm connecting this device through ethernet communication, so I guess I will try option 3. Thanks a lot for the tips guys.

Data[0] and Data[1] are 2 elements of an array tag called Data. The source specification is just telling the COP where to start.

Because it is an array tag, the elements are stored in sequential memory locations, in this case those elements are byte-aligned.

COP is quite a dumb instruction, and misuse of it can be dangerous. Essentially the COP instruction is a "byte copier", and just copies the specified number of bytes from source, to destination, regardless of data-type. The number of bytes copied is determined by the Length specified, and the data-type of the destination tag.

The only saviour to the damage that COP CPS and FLL could potentially cause if Length is wrongly specified is that the controller will cease the instruction when the destination tag boundary is reached, meaning it will not trample all over other tag memory in the database.

Here's an example of this in action... Both the source and destination array tags are only 20 elements long, yet the COP is trying to copy 200 elements. Notice that the processor is still running happily, and there is no corruption of other tags in the database.

nhatpham said:

I'm connecting this device through ethernet communication, so I guess I will try option 3. Thanks a lot for the tips guys.

Click to expand...

Only if you need to .....

daba said:

Data[0] and Data[1] are 2 elements of an array tag called Data. The source specification is just telling the COP where to start.

Because it is an array tag, the elements are stored in sequential memory locations, in this case those elements are byte-aligned.

COP is quite a dumb instruction, and misuse of it can be dangerous. Essentially the COP instruction is a "byte copier", and just copies the specified number of bytes from source, to destination, regardless of data-type. The number of bytes copied is determined by the Length specified, and the data-type of the destination tag.

The only saviour to the damage that COP CPS and FLL could potentially cause if Length is wrongly specified is that the controller will cease the instruction when the destination tag boundary is reached, meaning it will not trample all over other tag memory in the database.

Click to expand...

I understand what you trying to say. In another word COP will start and end at whatever length you assign then store it in a temporary INT. What about SWPB? Why do we want to use SWPB when COP start from data[0] and end at data[1] according to length 1?