Really Basic Data Logic Question

[gruntstripe 0]

Hi, My question is in the screenshot below. It's from Step7 lite. I understand that if you move, for example, a byte to a word the result will be padded out with zeros'. Or a word to a byte will be truncated. But I don't understand what is happening here. Thanks for any help.

[Moggie 17]

MW0 = MB0 AND MB1 MW1 = MB1 AND MB2 MW2 = MB2 AND MB3 etc Hope it helps? Steve

[gruntstripe 0]

Hi Steve, Yes I can follow what you're stating but I can't see why it is so. I would have thought MW0 = MB0 & MB1, MW1 = MB2 & MB3 and so on. Regards, gs

[JesperMP 2]

Now that would have been really confusing.MW0 = MB0 + MB1 MW2 = MB2 + MB3 and MD0 = MW0 + MW2 = MB0 + MB1 + MB2 + MB3 MD4 = MW4 + MW6 = MB4 + MB5 + MB6 + MB7 with merker addresses in particular, you have to be very careful that you dont unintentionally cross boundaries between separate addresses. It is very easy to do for example MD10 = MD6 + MD8 which has two cases of crossing boundaries. For words, always use even addresses. For doublewords, use quad-even (not sure if that is the right term) adresses. i.e MD0, MD4, MD8, MD12, MD16 etc.