Why would I implement a MEQ instruction compared to using AND?

What's the difference or benefits of using a "MASKED EQUAL" compared to using "AND" instruction? A "MASKED EQUAL" instruction is basically an "AND" instruction, so what's the difference? In the example below I got the same results

Ex.
MASKED EQUAL:

Source: 0000 1100 1100 1111 = 3279
Mask: 0000 0000 1111 1001 = 249
Compare:0000 0000 1100 1001 = 201

AND:
Source A: 0000 1100 1100 1111 = 3279
Source B: 0000 0000 1111 1001 = 249
Destination: 0000 0000 1100 1001 = 201

Dave85 said:

A "MASKED EQUAL" instruction is basically an "AND" instruction, so what's the difference?

Click to expand...

This is not correct. In an AND instruction you get a 0 as result when one of the bits in the AND is 0. In the MEQ instruction on the other hand, if there is a 0 in the mask this means the bit in the destination will not be changed. If it was 1 before, it will remain 1, if it was 0 before, it will remain 0. The difference between the two instructions lies therefore in the situation of the destination BEFORE the instruction as carried out. You're assumption is right IF AND ONLY IF the destination was all zeros on beforehand.

Kind regards,

The source and mask values are "ANDed" together.
This will screenout bits not on in the mask.
The value is then compared to the 'Compare' value. If the values are equal, the output is true.

http://thelearningpit.com/lp/doc/ncmp/intro-cmp.html

http://www.plctalk.net/qanda/showthread.php?t=1048

Thanks moggie, I was clearly referring to the masked move instruction and not to the masked equal. Your post reminded me of that.

Kind regards,

Dave85 said:

What's the difference or benefits of using a "MASKED EQUAL" compared to using "AND" instruction? A "MASKED EQUAL" instruction is basically an "AND" instruction, so what's the difference? In the example below I got the same results

Ex.
MASKED EQUAL:

Source: 0000 1100 1100 1111 = 3279
Mask: 0000 0000 1111 1001 = 249
Compare:0000 0000 1100 1001 = 201

AND:
Source A: 0000 1100 1100 1111 = 3279
Source B: 0000 0000 1111 1001 = 249
Destination: 0000 0000 1100 1001 = 201

Click to expand...

Technically if the Bit is Zero in the mask then it is "not looked at" so it dosn't care what state the Source is in. But the result would be the same. Both have to be a "1" to get a "1".

There is also the point that (in AB programming), the MEQ is a comparison instruction, and the AND actually modifies a value or writes to a destination.